This thread is a little aged, but I'm gonna throw in my .02 anyway.

If by complicated, you mean difficult, then no their songs usually aren't hard at all (at least for guitar players). They can get a little tricky because they usually have a lot of different parts, each with their subtle differences so it can be a lot to keep track of.

The whole time signature thing has never been a problem for me (and believe me....I'm not a fantastic guitar player) because I don't really pay attention to it. As long as I've got the bpm correct it's basically just focusing on the riff at hand and trying not to lose yourself in between all the changes.

The real trick is finding a drummer that can mimic Danny Carey...

http://www.youtube.com/watch?v=kAlcvIcjFI4 @:43....mind blown.