I'm at lvl 6 and it's getting tougher no doubt. Another thing that's pretty tough is Events in Master mode you have to play by pure recollection. I've never played rockband or any other games ever, so this is my first experience with a guitar game. This game definitely has a lot of venue to it and will keep me busy for a long time to come.
As far as the songs the game throws at you it's a curve either way to me because there are so many different styles you have to learn. I'll take it as a challenge crappy or not I'll play'em just to get more practice in, added with a little variety. Right now I'm doing the EpicCenter Events it's a six song set list RS threw at me:
Spider & The Fly
Good Enough **
Run Back To Your Side **
We Share The Same Sky's
Under Cover Of Darkness
House of the rising Sun **
To me the way this game just throws out songs is pretty crazy this would test even the most seasoned vets. The interface is probably the most challenging in itself meaning it's complicated because as you progress it throws out extra notes. And the way it comes flying at you is just to fast for me, so I usually ignore it until I can sponge it in later in the song. Gobbledigook by Sigur Rós was a pretty lame song to play and listen to but I went ahead and plowed through it regardless.
I haven't run into any issues yet as far as losing my qualifying songs for the Events, but then again I always go into the venue and test the waters. Once I'm in and if I play the first song lousy I'll quit the Event. From there it will go into it's save mode if I exit out to the game menu. So make sure you always save before you pull the plug on this game. So far the game hasn't crashed or lost any Q events it's pretty much been flawless as far as bugs on my end. I do have the latest build Xbox but doubt that would have any impact but who knows