Am I the only one who loves using the Gravity Slide? Especially on the challenges; it just feels right once I got the hang of it.
No, you're not. I'm a fan of the gravity slide as well!
I know SmithnCo said above that didn't care for the tilt mechanic. I thought the same thing at first, but after a little practice I grew to appreciate it.
It does appear slightly "gimmicky" at first, in that you're asked to hold two locations on the screen and tilt the system to move. You have to learn to "steer: Kat almost like steering a car. When I first started using gravity slide, I had a tendency to tilt too hard and oversteer. However, after a few tries you should get a good idea of how much tilting you need to do.
Also, as KalBalboa pointed out, try to learn how to drift (lift one finger off the screen, keep the other one on). I used to do the "stop and turn" technique a lot early on, but if you can grasp drifting, then you'll find it to be very useful.
On an unrelated note, I got the "Frequent Flyer" trophy yesterday! I accomplished this in one of the early challenges in Auldnoir. Flying and attacking all those enemies in succession was a lot of fun!