I played both Gothic I and II and found them to be amongst the best RPGs I ever played (up there with Fallout, BG 2, and Planescape Torment). The controls take some getting use to, and the beginnings are HARD. Combat feels clumsy, but you start completely unskilled. Once you get some levels under you, it becomes much smoother, and actually exciting. I found it to be a nice balance between strategy and twitchy action (which I suck at). I didn't find the game noticably buggier than any other computer game - certainly nothing showstopping.
The storyline is great, especially for Gothic 1. The NPCs are memorable, with solid voice acting. The world feels real. The games are very open (especially the 1st one). I would find myself just climbint to the top of a mountain just to see the view. Oddly, I found the world more vibrant than Morrowind, even though the graphics were inferior.
I've actually been toying with the idea of converting Gothic to a paper rpg (setting, not the ruleset) - it was that good.
However, when I lent the game to other people, they were not as enthusiastic as me so take my advice with a grain of salt. Some people love it (see rpgdot.com), but others are indifferent. Fortunately, you can buy Gothic 2 Gold really cheaply these days, though it's a better experience if you can track down Gothic I first (out of print).
