I have learned to basically trust Rottentomatoes on most genres of movies. I do find it to be fairly accurate within reason, except when it comes to comedies. Peoples' comedic senses are so different that it may be impossible to put a fair score on them. Some cheaply made comedies with nobodies for actors I personally just find hilarious. While on the other hand, I find most comedies with a 90+ rating to be overly safe and/or politically correct and I actually avoid them usually. Anyone else feel this way? Just curious.
Also, if it weren't for Rottentomatoes, I'd definitely watch a hell of a lot less movies, because it makes discovery so much easier.