Someone asked which quests have broken, let me just put it this way, all of them have broken for someone. I reported all of mine here and just had to give up on my first build after 150 hours of play because of it. I done talking about broken quests, I'm done arguing with f@n boys about how the game was released before it was ready and I did enough free testing for Bethesda. I've started a new chapter in my gaming life and it doesn't involve any of that crap.
Here's what I suggest; look at your first play through as a test. Play however you want do whatever you want see what breaks, learn the games quarks, just don't get too attached to that character. What you really need to do is learn how to play the game, and I'm not talking about not fast traveling or regular sleeping habits or any of that sillyness. Just realize that if you go places you haven't been sent to on a quest you run the risk of of breaking a main questline. Imagine you are playing a Nord warrior and the companions quest breaks, it's pretty much game over and after 150 hours you might be a tad upset. Use the UESPwiki whatever you do.
All that being said this game is amazing and is the best gaming experience I've ever had hands down. Hope you enjoy, cheers.

end up doing the same dungeons twice which could take some of the fun factor out. But being disciplined enough to walk straight past a dungeon that I've stumbled across will be pretty tough...
