Wow! I really enjoyed this one.
Fighting the enemies felt really good; I loved that three-part attack thing. The sound, the particles and the little jumps you do really make it feel great to kill enemies(which is good, since you do it a lot).
I never got lost or anything, as every area unlocked the next area through some new ability.
The final boss-fight was cool and well-balanced I think. All the health upgrades helped there.
My only minor complaint is that the phase-ability didn't feel like it was very meaningful. It's always used to solve the same problem in the same way. It's only a minor complaint.
Overall I thought it was real fun, I love games of this sort! :)