Baracuda,
You are right that it is spread across a wide spectrum, but in fact some systems only use a few of the channels when in use, and this can be a problem. If you power up your Tx and it chooses two channels in the 2.4 spectrum that are near to each other, and then during flight someone powers up a strong 2.4 system (like for Video broadcast, FPV or something like that), and is sitting over your channels, it may overpower your signal and cause a glitch or crash. If the system frequency hops, then the liklihood of this is decreased. Also, some hopping systems choose one of 11 frequencies in the band, while others may grab more (maybe 80 like FASST). There are differences. I would recommend reading the following post by Bruce on RCModelReviews.com

http://www.rcmodelreviews.com/spreadspectrum01.shtml There are a lot more reviews and articles on his home page that I would recommend reading. It's very informative.
Curtis