After 1 official patch (9/2/14) that I'm aware of, this game has very few bugs (compared to KB: WOTN), w/ the caveat that the Mac version seems to be a little behind the PC. I'm expecting a new patch soon, and hopefully the Mac faithful get a better game. Because this game is super fun.
I was mystified to read some reviewers thought it the worst in the series (or maybe the "weakest"). That's not my impression at all. I think they stepped up their game significantly w/ the writing, quests, and overall sense of humor. Also, for those of you tired of playing the same old standby human and dragon units, this is the game for you. You can of course over time get a significant medley of old favorites, but I would recommend trying to stay close to the thematic choices that fit the 3 PCs: Mage (Vampire) > Undead units; Paladin (Demoness) > Demon units; Warrior (Orc) > well you get the idea. I've only played as the Mage, but I suspect I won't feel differently after playing the next 2 PCs.
More than past games, you really should have a pad of notepaper, and keep notes on where NPCs are, what they are selling, etc. A lot of times, the main clues for a quest are in dialogue only, so pay attention!
There is a massive amount of bang for the very modest buck you pay out (I'd go for the Premium Edition for the 2 new islands, 1 of which has a cool new unit). I spent a ridiculous amount of time on just 1 playthrough, and I plan on 2 more to come.
There is one particular new unit that is one of my all-time favorites: the Dragon Rider. They cost a fortune and are hard to get initially, but--at least for a small army game like the Mage/Vampire has--they were a huge part of my success mid-late game.
There are minor criticisms I might have, but that's all they are--minor. If anyone cares what I think, here they are:
1) while underground "realms" get maps, dungeons don't; that should be an easy fix going forward in the series;
2) changing the camera's perspective can be a minor pain, sometimes having to poke your horse into a wall and swivel around just to see from a different perspective;
3) the "bleed" damage is OP in this game. All it takes is some puny archer to hit your Black Knight stack and all of a sudden you're losing numbers of them from what should have been a minor wound;
4) on a similar note, I wish they would calculate damage/status effects a tad bit more "realistically"--for example, it's great that Ents take double fire damage, but why should any of the undead units take "bleed" damage? Silly.
Don't get discouraged in the early game when you seem limited in troop recruitment etc. Once the game opens up (i.e., other islands and realms), you'll soon have a dizzying number of potential quests. Final nice point: many times, there are more ways than just 1 to solve a quest.