The enhanced edition is an improvement, for me. It adds, amongst other things, a search bar for the journal (which was otherwise a pain to use) and the ability to zoom in and out, which I didn't expect to find useful but ended up quite liking. It does not as far as I am aware, add jarring new content or make story-related changes. Perhaps Beamdog have fixed lots of bugs, but I still find that it crashes to desktop periodically, and worse still, conversation bugs that can render the game unwinnable still exist (or have been introduced). As an example, in the lead-up to the final area of the game, during a significant conversation, instead of conversation options it presented NO VALID REPLIES OR LINKS which when clicked on ends the conversation -- without progressing the story. All in all, if you are considering buying any form of this game (and I think you should), I still recommend this one. If you have played it before and are unsure as to whether you can be bothered with the bugs, and want to know whether it's all fixed these days, then maybe don't bother.
This game has a great deal of potential, but for me it has always been unplayable because of the huge number of game-breaking bugs. There is a popular and extensive mod pack (the Circle of 8 Mod pack) that (I gather) fixes a lot of the bugs. However, to give an idea of quite how bad it is, even with that installed, when playing through the tutorial, upon moving from one area to another, the game instead loads one of the later areas from the main game. This is the third time I've tried the game. On the first, I got a few hours in before giving up -- not because the game isn't fun (see other people's reviews), but instead because it's just not worth putting up with corrupted save files, inexplicable teleportation, inventory items popping out of existence depending on which order they're clicked on... I suspect that if one is able to somehow avoid these problems -- and maybe it works better on some operating systems than others -- then it would be quite fun. The music is great, and the game looks good.
