I'm about 10 hours in and haven't encountered any serious bugs yet. I didn't start playing until v1.2.5, though, so the worst bugs were perhaps already patched before I started. The worst that I've encountered is a conversation in which our two character models were intersecting, but that was just a visual thing.
I'm not the biggest fan of the 8-hour-long prologue. It was very scripted, had little user choice, had too many cutscenes and was a little sappy. It was done very well; I just feel that it was drawn out too long. I'm glad that it's over and relieved that the game appears to be more like an open world RPG after that point.
It feels like a more realistic Oblivion or Skyrim, though it's a little more cinematic, like a Dragon Age game. There's a bit of a dichotomy, though, between the character that you're given and the choices that you can make, IMO. Your character is established as a sweet, principled young man, but, early on, you're given many chances to steal, lie and bribe. In fact, I'm not sure if it's even possible to complete a quest that you have to complete to progress without doing one or more of those. The game almost sets you on a path to be a bad character, yet, even when you're choosing to do bad things, the character expresses doubt, hesitancy and naivete. It feels like the game is conflicted between the necessity of the character being a goodie-two-shoes for purposes of the story and the desire to allow the player the fun of doing naughty things. I recognize that the two are hard to reconcile, but it would've helped to have not made it so easy to go evil so early on. If you're really big into immersion, you may want to resist as many temptations to go bad as you can, so that you can play as the goodie-two-shoes that the dialogues and cutscenes make you out as.
On the subject of the world, I appreciate the strive for realism, but it does feel a little empty, not dynamic enough and not interactive enough. It could use more animals (especially birds), more weather (wind would be nice) and more things to pick up. Locations and the distances between locations become much less interesting when 99.9% of all objects are fixed and can't be moved or interacted with. Contrast that with, say, Skyrim, in which, if you enter someone's house, just about every plate, pot, utensil, candle, book, barrel, left-out food and so on can be used or picked up and stolen, even if it's completely worthless. In KCD, most of those don't even register as things that you can interact with. Pretty much the only thing of interest and worth interacting with in most buildings is the chest.
I've given only criticism so far, but it's still a good game that I'm enjoying. I really like the historical setting and realism. Most RPGs are only pseudo-historical or completely fantastical, so it's quite nice to finally have one that is grounded in actual European history, and a setting (Bohemia in 1403) that's a bit different than the usual. I also appreciate the art style, as well as the care put into the various systems for buying, haggling, lockpicking, pickpocketing and so on, and all of the various stats. It's definitely a full-fledged RPG, which is a relief, since it could've been easy to make a more action-focused and cinematic game. I guess that what I'm getting at is that, so far, it's a game worth grabbing and playing eventually, though some people may want to wait for it to come down in price first.