Finished it yesterday.
For anyone who cares, here come Gord's Neutral-Positive (tm) impressions:
When inXile made the Bard's Tale 4 Kickstarter, my main reason for backing it was actually that it came with a free copy of Wasteland 2 - a game which was not exactly considered the greatest thing since sliced bread by the Codex. Nevertheless, I was curious enough about it, but being the cheapskate I am, obviously I didn't want to spend too much money on it. Having another potentially interesting game on top (BT4 itself) sealed the deal for me.
I knew about the original trilogy, of course, but never considered myself a particular big fan of the games (and did, so far, not play part 3). As such, I also didn't have any super specific expectations when it came to BT4's gameplay and/or content beyond it being a blobber/dungeon-crawler in a vaguely celtish-inspired fantasy setting. IMO, it was clear they wouldn't deliver a faithful, carefully modernized new iteration of the old games' formula, but rather something different right from their Kickstarter pitch.
Consequently - if you expect and demand just that, better avoid BT4.
A few weeks before the release we also saw the release of another offspring of the BT4 Kickstarter: the first part of the original trilogies remaster, which for some time looked unlikely to ever see the light of day.
I played through that game shortly before BT4 and found it to still be a fun experience, if rather simplistic and a bit grindy overall.
Anyway, BT4. As everyone noticed quite fast, inXile botched the launch. Hard. So much, that one might actually wonder if they purposefully tried to commit financial suicide there.
The game released with horrible performance issues and a big number of bugs, at least one of them preventing the game from being finish-able at all (little did we know then, that the prize for the buggiest kickstarter-release 2018 would actually be claimed by Owlcat's Patfinder:Kingmaker only a few days later).
The Steam ratings consequently quickly reflected the poor release state of the game, with one of the major complaints being the technical issues of the games.
Luckily, for me the game was playable enough on my mid-range gaming toaster, even though the framerate was much lower than one would expect from the game's graphics. I also got spared from the worst bugs (I think the game crashed a total of 3-4 times over my entire playtime and I could complete all quests).
Patch 2 and 3 have since improved the framerates in many (but not all) areas quite a bit, and also fixed many of the quest-related bugs.
Still, while being quite playable, in terms of performance the game still has some way to go, imo.
Another of the somewhat difficult to understand decisions inXile took, is having start the game in one of the actually ugliest areas - Skara Brae proper. As mentioned also by felipepepe, it's a rather uninspired grey-and-brown run-of-the-mill fantasy town. Apparently the release build defaulted to low graphics settings for many, emphasizing the bland looks further.
To inXile's defense, patch 3 has improved the situation a bit, overhauling the lighting of both Skara Brae upper and underground.
For all non-graphic-whores that managed to keep playing, however, the first real dungeon that players would encounter (Kylearan's tower) is a pretty different story. It offers several nice vistas and an overall nice mix of BT4's main gameplay elements: combat, riddles and exploration.
While the combat is nothing I would call very complex, I found it to be fun enough most of the time - and it's certainly more involved than the even simpler iteration of the original trilogy.
The biggest issue I had with it is that it only worked really well until around half-way through the game. At that point, the player has encountered most enemies and probably skilled a party that can deal with most of them easily and without having to adjust the strategy too much. Sooner or later the player will likely be steamrolling 99% of the encounters (which is actually faithful to the original games).
I would have, however, liked a way to flee from combat or change the active skills, which are limited to 4 per character - e.g. by giving up my own turn. While this doesn't matter later in the game, esp. early on some encounters could be very difficult without the right skills.
The different types of riddles/puzzles play a much more pronounced role than in the old games. About 95% are made up of the 5 main types: stone-block-pushing, fairy golf, power-line routing, celtic-knot-turning and shifting around of turning gears. They are usually not very complicated, although a couple of them might have you ponder over them for a few minutes.
The exploration part has you finding secret doors/passages and solving puzzles for loot. In the best moments, the different elements work nicely together, creating a good pacing.
In the not-so-good moments, inXile just put several puzzles of the same kind one after another (albeit usually with increasing complexity), without doing much to shake the routine up a bit. Luckily that is limited to only some areas in the game.
The character system is, again, not a very complex one, but I found it serviceable enough. Sure I wouldn't have minded a more elaborate one, but then again old BT didn't exactly have a very complex system either, so maybe it is a bit unreasonable to expect too much here. At least you can actually influence your characters progression this time around...
You start the game with 4 different classes at your disposal (bard-fighter-rogue-practitioner(spellcaster), which can be skilled in different ways over the course of the game. Each character class typically has 3 or 4 tabs containing a tree-structure of skills and upgrades. An additional skill tab can be unlocked later in the story for another special set of skills. Each level-up, you get 1 skill point, which can be used to unlock a node in the skilltrees. Nodes range from simple stat-bonuses, over active or passive skills, to capstones, which give certain special abilities to further differentiate characters a bit.
Since you will accumulate quite some level-ups over the course of the game, eventually the really useful nodes will be taken, so you might find yourself taking boring stat-bonuses or skilling characters increasingly similar towards the end of the game.
Stats are, with the exception of those gained from the respective skill-nodes, almost exclusively governed by equipment. Con translates directly to HP, Int increases damage of mind-spells and helps you resist mind-damage-spells (important for channeling abilities), Str increases all other damage. Each piece of armor or weapon will give a bonus to those stats (and sometimes armor for flat dmg reduction, or additional spell points), and some, in particular the uniques and puzzle weapons, come with special abilities (like unique active skills, special buffs/debuffs or a bonus to another skill).
About the other much discussed features of the game, the limited save-system and missing respec, I can only say that I didn't care.
There are usually enough spots to save, the game saves on exit (will be deleted on load, however), so no danger of losing content because you have to go to bed/work/shopping/masturbate. Admittedly it sucks if you lose progress due to a crash, but that did rarely happen for me. And concerning respec, I just didn't think it was necessary.
Overall, the game is a somewhat uneven one. You start in the most ugly area of the game, yet they do have some very beautiful areas, so it's not that they totally lack talent in that department. A similar thing can be said about character/NPC models - humans and elves look amateurish, while trow, dwarves (well, from a technical PoV) and most enemies actually look quite decent.
The combat is fun especially early on, but eventually becomes too samey, also because they hardly shake up enemy encounters after about mid-point of the game.
In the best areas, they get the mixture of the different gameplay elements just right, in other areas, they overly rely on repetitive single elements.
The decision to (slowly) unlock party slots is also something many people understandably have criticized.
Conclusion:
In total, I would rate it 6-7/10 - it's good for what it is, but no great, soon-to-be classic masterpiece.
Still, for some reason, like an 80s action B-movie, the game had a certain charm and was mostly fun to play. Oh, and the music is quite nice (even if I would have liked to stuff Rabie's guitar into his mouth after the 10000th rendition of Snow in Summer).
I certainly don't regret having backed it (I didn't mind getting WL2 and BT1-3 remastered out of it, either).