I bought the game last Friday when it came out on GOG and finally finished it yesterday. Overall i'd say it is your "average good game" in that it isn't anything great nor will ever be a classic but it isn't anything mediocre or bad either - just one of many games that are merely "good".
I do not see games as the sum of their parts, instead some parts can be elevated (or lowered, but that only happens if i dislike something a lot) based on other parts and Vampyr is a good example for that: i really liked the setting and atmosphere, which in turn made me not mind the combat much. The combat is functional, in that it is there and works, but it isn't anything special. My entire "strategy" for the combat was to raise out my claw attack, stamina bar and blood pool (in that order, more or less), upgrade a machete i found and a blood sucking secondary weapon (i don't remember the actual name) and then all the fights were either one shot claw kills or claw-suck-suck-suck-repeat with the occasional dodge. I'd find that boring in other games, but here i liked the setting so i didn't mind it much, though i never really "liked" it.
As i wrote, i liked the setting even though the 'dark foggy 19th-20th century London at night' is sort of cliche in gothic stories. Being a vampire doctor who specializes on blood transfusion research and trying to find the cure of an epidemic that ravages the entire city is original (or at least rare enough for me to not have encountered it before or be able to come up with a previous case). Sadly there isn't much "research" going on gameplay-wise (i sort of expected to see all the bits and crap i pick up from fallen goons to somehow be used for researching, kinda System Shock 2-style though without the delay since there isn't any computer at the background here :-P).
The main gameplay loop seems to be running around the city (which i quickly got bored of, especially near the end where you sometimes have to run across the entire game world), exploring the environment in the areas where people live (which i liked it as i love to search every nook and cranny for items in games and the reason i do not like most open world games since they tend to have a lot of useless filler content - but in this case the world is clearly divided into "people" areas and "enemies" areas and the interesting stuff is almost always on the "people" areas that are relatively small) and finally talking to people.
This "talking" bit is an interesting idea although due to the way it works it kinda makes the game feel like a dating simulator where you are trying to figure out what sort of response the person you are talking with would like to hear based on whatever caricature the character is supposed to be. And this last part is one of the weakest things in the game for me - while there are some interesting characters, most of them feel like caricatures - especially the supposedly bad people who often look and behave like cartoon villains (e.g. the "xenophobic landlord"). In general i found the dialog for most characters to be poor (and it has one of the most laughable depictions of depression i've seen in a game to the point where i thought the character was just a complaining edgelord - i mean his idle line that repeats every so often is "even my dreams are soaked with gloom" - but no, he is really supposed to be depressed instead of whiny). There were some exceptions and i think most of the main characters were generally good.
On the other hand, even if the dialogs were often bad, i liked their almost theatrical style (though the voice acting was hit and miss, especially when in some cases it was clear that different lines on the same dialog were not taken in the same session and had different tone). I don't know if it was intentional or a result of trying too hard to sound early 20th century, but i think it fits the game.
Also even though the dialog and characters weren't great (with exceptions), i liked the overall story and the world they built - i'd certainly like to see a new game on the same world (though the story for this game is self-contained so any new game should have other characters - it isn't like the world doesn't allow for that). The ending was a bit... well, not unexpected as it was clear what will happen, but it felt a bit like a shoehorned result due to me not being a full pacifist. Perhaps if i try to play a non-lethal run it'll make more sense. That will not happen any time soon though, if nothing else i'd like to get a new GPU first because i ran everything and mid-low settings and even then the game was around 40fps (i have a very low end PC and an integrated GPU or "APU" as AMD calls them).
The whole "your actions have consequences" didn't look to be very deep either. I've only finished it once, but from what i understand most dialogs barely change anything and even killing some people (outside the community "pillars") all it seems to do is readjust the available merchant prices and items. And it is buggy (or at least misdesigned) too since i had at least a couple of "sidequests" (as much as you can call these quests anyway, you mainly just find random stuff on the environment) where i didn't talk to the right people at the right order so i failed the "hint" (e.g. picking up an item i randomly found, talking to someone later who apparently lost that item, but the game was written so i'd have to talk to another character to learn about the item first, so now i lost a "hint" with both characters).
Still, despite the issues it has, i found it entertaining - largely for the exploration, world/setting, story and overall atmosphere and less for the characters and combat and i'd like a new one. It isn't a game i'd recommend at full price, but i found it worth it the ~18 euros i paid for it on GOG.