Tried a match briefly, but my crappy wireless connection forced me to leave lest I lag it up for everyone. My first impression was 1) it feels a lot less like Sonic and a lot more like a regular FPS, and 2) for me personally, that's a bad thing - I suck at every FPS I've played, and could never come to grips with mouse control.
I have fond memories of throwing rings around in small, symmetrical levels, using 100% keyboard control, and - occasionally - even winning a game! That's clearly all in the past, but I'm ok with that. :) For most players, who don't share my limitations when it comes to FPS games, or my fetish for symmetry, I'm sure the changes are all to the good.
Thanks for the thoughtful replies, everyone!