I've been playing GOTY Edition since the week it came out last October. I'm probably 300 plus hours in - I haven't done much of the main quest yet, but I've completed an absolute ton of guild quests. I still haven't gone to Solstheim or spent much time in Mournhold, so that's more stuff I've got to do.
It's irritating though, that there are certain quests I can't complete because I spent the first 50 so hours of play just wandering around, finding hideouts, killing everybody, and taking their shit. This is plenty of fun at first, but here's a tip to anyone just starting out in Morrowind: don't do it until you've done all the guild quests you want! There are a number of things I can't do now because I mislaid an item, killed someone I needed to talk to, etc. Anyway, probably the best game on the Box, in my opinion. I'll probably be close to 500 hours before I put it down.