This is pretty decent for your second animation submitted to Newgrounds, in my estimation. There's certainly room for growth, but I like what you've done so far. The music sounds very nice (and I don't just mean mine); you actually animate your drawings without relying heavily on tweening; and aside from a bit of gratuitous gradient usage, your drawings are pretty solid. I see some complaining about the fact that it's another Sonic fanimation, but there are quite a few fans of the Blue Blur around here from what I've seen, and I even fulfilled a music request for a remix of Splash Hill Zone Act 3 back in 2011. You should check it out sometime. ^__^
I'm looking forward to seeing what you can accomplish now that you have a new tablet to work with! I don't know if you've got your heart set on only presenting your AU version of Sonic for now, or if you have other ideas percolating as well, but if you expand into other realms you could quite likely increase your demographic. I'm happy to become your 15th fan, and maybe you'll be generous enough to repay the favor. If you act fast, you can be #150! ;)
Best of luck going forward!