[a] is a lot easier than the others, lol. I can do the double scales better than the single note scales, for some reason.
Plus, the thing that's really a problem for me is scratching. I can do the easy stuff, but anything with semi-frequent scratching kicks my ass.
Also, Era [a] is ridiculously fun. But I'm not going to pass that any time in the next millennium :/
Oh, and anyone who says 5.1.1. [a] is a different song should listen to the background music in the easier versions more... It bugs me when people say it's a totally different song, and stuff like that. You just play like, 90% of the sounds, in the [a] chart. (and what the hell was konami thinking there? lol, 1 on all other difficulties and a 9 on [a]? lol)