Yeah, I'm not sure why they did that. If you didn't pre-order it, it was pretty much impossible to get on release.
I actually managed to 5 star all the songs on medium. Stricken and Raining Blood kicked my ass. Medium to hard is a tough transition for me because I suck with the orange button, but I'm working on it.
The songs from the store SUCK, but overall the songs they put in the game are pretty good. Even some of the newer songs from the last few years aren't too bad.