I own Sacred 2 and haven't touched it in months, but I liked it when I did play it regularly, it is addictive. I had it regularly crash on me after a period of game-play, without the elite textures pack (because there is such a textures pack available, it's official too, but don't bother with it, first because it's a big download, and second because it barely makes any visual differences between the default maximum in-game settings and the elite textures, additionally the elite textures cause instability problems).
If you do buy Sacred 2 anew, then yes try to get the UK version which includes the expansion pack, which by itself updates the original and the engine a bit from what I had read, and it does indeed help make the overall game more stable. With that said, I did eventually stumbled upon a good in-game tweaking for the settings to make vanilla Sacred 2 more stable, which simply consists of completely removing the grass, not using the elite textures pack and finally to add a launch command to the shortcut which happens to be " -nocpubinding " I believe (without the quotes), and finally, still highly recommended is to run it under Windows XP SP3 compatibility mode, especially with Windows 7, but is also recommended even with Vista (which is what I've done).
Under those settings I've been able to play without crashes for many hours, but as I said I haven't touched the game in months due to lack of interest, but I still got two characters in my saved game and I do plan on resuming my games eventually, but the game world of Sacred 2 is Very big, with a capital 'V' indeed, and I don't particularly refer to the number of side-quests available (which is numbered to 500+) but the actual "surface" (explorable) on which everything is set... it's just extreme, you'll understand better when you play it, don't try to rush anything, it cannot truly be rushed anyway (well yes it can, but it'll still take you days before completing the main quest).
Overall, for me, the plus and minus points of Sacred 2: Fallen Angel are:
+ Great atmosphere, supported by very beautiful graphics (on highest settings)
+ Good variety of skills to end up with different character builds
+ A crap load of items to find including specific Unique and Legendary ones
+ 200 Levels (yes, 200 Levels)
+ Multiple difficulty settings (good increase in difficulty, but items drops are better)
+ Good enough variety of characters to chose from
+ Most of the music is generally good
+ Sounds, enemy taunts and weapon effects are good
+ Gargantuan-sized game world, 500+ side-quests (excluding the expansion pack)
+ Each world locations are unique-looking (excluding some dungeons, caves, etc.)
- Instability issues (varies a lot apparently, some report barely any issues)
- Character's taunts/dialog isn't serious and down right silly at times
- Main story is weak at best
- Side-quests, while numerous, are often repeated variates of basic requests (go take 'x' items, bring it back, find lost NPC, rescue NPC, kill specific monster, etc)
- Lack in variety (not quality) of character and monster animations for attacks and kills (things like that don't go by unnoticed by players like me)
- Game world is so big that it may intimidate/discourage completionist players around who intend to finish every single quests and discover everything that can be (minor negative at best, but still a possibility)
- Good items drops highly dependent on the difficulty setting (making the first setting, namely Bronze difficulty, basically useless, highly recommended to start right at Silver difficulty)
So, is Sacred 2 good? I would give it a solid 6 / 10, it's passable, it's enjoyable, you could want to come back to it and resume your games, but there's better out there.
Hope it helps!