Like what you hear? You can download the individual songs via The Mega Man Network. Personally, I think it's a rather nice score, especially for a mere mobile title... and a puzzle game, at that!
Of course, one can't talk about Puzzle Battle without some mention of its artwork -- the icing on the cake. Its visual style is definitely something I'd like to see in a future game, IMO. It'd make for an interesting change of pace from the recent pure 8-bit ventures. Maybe it's just me, but I can't quite imagine a Mega Man 11 with entirely 8-bit visuals again. It was unique the first time around, but a third retro-infused outing might be pushing it. I sort of envision Puzzle Battle's style as a middle ground when it comes to nostalgia; it's retro, but just modern enough to appeal to (mostly) everyone.
Mega Man 11 might just benefit from mixing things up a bit visually. Something along the lines of the above might be the safest, and more "faithful" route to go. You can't please everyone, but hey, it's something different.