I've learned to not pay the difficulty ratings too much mind. I've had a harder time learning some "3 guitar" difficulty songs and pretty much breezed through some "4 guitar" songs.
However, I do have to say though that seeing the "5 guitar" rating on the Boston songs kind of put me off - there aren't many "5 guitar" songs on the site, but those that I've looked at were beasts!
So I think I'll give this a try... :-).