I personally am not a tremendous fan of discs in general. That being said, I can see where they would be beneficial for some people. It depends on what style of riding you do. If I were to get discs I would either get the Avid mechanicals or the new XTR discs. The XTR setup is about as light as it gets but is only a two piston setup, whereas the XT setup is a 4 piston. From a pure maintenance standpoint (i.e., just bleeding the darn things) XT is much easier to deal with than Hayes. Avid is also coming out with a hydraulic brake soon which may be worth the wait.