Good...could be EPIC.
My main problem, which I know you've probably heard is the LENGTH of the game. It is way...and take this seriously...WAY too short. I thought that it would be at least 10 levels from garage to concert. (and even this is short)
I liked your style, it was very user-friendly. I am a comp-gamer so it was really easy for me to get past all the levels. SO my next concern is difficulty. I was expecting to have one part go up and down notes, from the left all the way to the right with notes. It would have been fun and a bit more challenging. If this was a keyboard game...it'd be even more easy.
Additional Suggestions:
"Rags to Riches" mode
"Able to customize guitar/player"
LIKE the other guy: Different instrument but keeping within band
Getting to sign and make money...as well as managing a band.
The last one is a little over but bottom line.
Make it harder and longer (LOL! sounds wrong)
and it will be able to live up to the name.
TENACIOUS D FTW.