I personally don't think Rush and Rush adventure were worth the buy. Get Sonic Advance, and skip the other six or so Sonic games on Nintendo handhelds, the rest drifted a bit too far. That's a little off topic, though.
This game could be one of the better Sonic games in recent years. I agree with what was said about Sonic and the Secret Rings above: The stages where you get to actually play the game without a twist or an annoying goal were fun, but the controls and issues with all the challenges made the game intolerable. I couldn't finish it, I played it, and after about three or four hours, I just couldn't go on. Some parts were a lot of fun, but others weren't so much.
This game has potential for a few reasons, the first of which, it likely gets rid of that annoying Homing Attack, which is part of what destroyed Sonic's platforming in the Adventure era (Press jump twice to kill anything that's not a boss and as a freebie to connect with springs, so you don't have to aim to get to them.) Without the homing, attack, though, Sonic's control in the 3D realm is too imprecise to easily destroy enemies. It is my believe that the sword is compensation, giving Sonic extra attack range. Quick swordplay can easily fit in with Sonic's style, as well, as long as he doesn't have long, elaborate combos.
We'll see what else comes from this.