I played it a bit and I have mixed feelings. There's a demo if anyone else cares. Its not a 1:1 copy or strict improvement of an existing Heroes game, its got a mix of different elements and it works as a spiritual successor.
Towns spawn six units, all of which can be upgraded, but it also uses Heroes 4 system for some units, where you can choose a different unit in that town. In the town I picked, which was a modified version of Castle/knight towns, in the 5th slot, I could choose cavaliers or crusaders, one of which had the opportunity to move faster, the other was generally stronger. The top tier unit here was a griffon, curiously. Also, while this was the closest to a traditional Heroes town as I remember it, I haven't really played anything after 4. The rest of the towns, while the usual Heroes 3 fare, are vastly different to what they should be copying. I primarily fought against a town that used dwarves, which had dwarves that had guns and magi dwarves. Towns did not have any menu graphics, instead being simple build menus. Interestingly, if an enemy is close enough to a town, the castle walls appear should you attack.
Heroes fight in battle, and can die, like in 4. Unlike 4, you can only have 1 to a party. Heroes can of course retreat, but unique to this game, so can units. Recruitable heroes are tied heavily to the town they were summoned in, and it seems likely you can only recruit heroes that are directly aligned with the town they're associated with. Level-ups increase skills, which function as a reverse pyramid, increase skills at the top, and you can increase skills lower down. These skills range from typical Heroes ones, like scouting or money-making; To unusual ones, like decreasing the cost of buildings or units; To combat ones, like directly increasing the hero's abilities to one aspect of units combat abilities.
The good:
Keeps/treasuries combine the banks, having resources to pillage, and unit dwellings.
Units can move on their own.
Garrisons, that is garrisons on the map, automatically get troops whenever you conquer them. I don't think this comes from your heroes stocks.
New neutral units gradually spawn on the map, AND they create resources when they do. Also, all armies create resources when they're defeated.
There are neutral roving armies on the map. They don't steal anything, they're just there for punching practice.
Combat is interesting. I haven't really figured out much of a strategy yet, but the game manages the chaos well. You have the usual spells, and you can pause the combat. The game protects itself from going really crazy thanks to a weird limit system I don't understand. You have a variable amount of unit points, and units are worth anywhere from 1 point to around 10. Frequently these points were in the 150 range. Your units will gradually spawn in (you have no choice where), so this only chooses your opening salvo.
There are some interesting spells, one of which I had to deal with the most was a spell that turned units into frogs. There was seemingly no way for me to counter this, and the AI without fail used this on my crossbowmen.
For those of you worried about proc-gen, there are a limited number of pre-made maps. I can't speak to their quality, I only did a proc-gen map.
In town combat, you don't get a catapault, instead your units literally tear through the walls.
The bad:
After quitting a long session the game basically crashed my entire system. I have 16 GB of ram on my machine, and this hungry bastard wanted all of it. Now, this was only a problem when I quit, but still. Really screwed up the computer for that session, going as far as to make everything slow. This can be solely put at the foot of the author, since it seems like this is an entirely original engine. I suspect this is some memory leakage in-game, probably to do with fights.
I was on the lowest difficulty setting, and while the AI wasn't beating me, it was pretty close. This might be because the map didn't really give me the proper resources. The AI had access to the latter units far, far faster than I did.
At the start of a week unit dwellings create a caravan, which automatically goes to whichever hero is nearest it.
Short water tiles seem to be completely broken, as I nearly lost the map because the AI ran across one, and I chased after him, assuming it was just an improperly done river. Nope, actual, freaking, water.
This game can really be described as a Heroes-like, far, far too much. The overmap, outside of the exceptions, is exactly like Heroes 3.
The obelisks don't tell you things based on pictures, they tell you things based on text.
The character artstyle. The heroes all look awful, and the units don't look much better. In motion they do that ugly little jumping on each leg people animate a character doing when they don't want to animate walking. While I feel like the overworld artstyle is decent, there's no redeeming the characters.
I can't really comment on the proc-gen of the engine yet, I've only played one game.
I like it, but I can't really recommend it yet. There's no guarantee that this game will stop at 16 GB, and will only try to consume more and more RAM. If he fixes that, I think it could be a pretty good game.