What would really be cool is if it could be the same kind of risk-vs-reward thing that the spindash and (forget what its called at the time, the figure eight thing, y-know) system in Sonic CD had. Namely, one provides an alternate way to speed up, but its more risky because you're not rolling (which means no ball physics), you can get hurt if you are careless (it is possible to jump over if you don't mind losing a bit of speed, or you can drop into a spin), and you tend to go faster on ground which means you're gonna pass by interesting new paths.
That's the Super Peel-Out, I believe, and I personally don't want it in this new game. Perhaps I'm growing tired of ubiquitous boost panels and the boost mode of Rush and Unleashed, but I want Sonic to
work for his speed in this game by exploiting natural momentum, not to have it instantly accessible.* And the Super Peel-Out falls into the category of instantaneous speed maneuvers and objects, though that's slightly obscured by the fact that the move requires a brief charge.
I do support the inclusion of the Super Spin Dash though, in part because I do not regard it as a speed-centric move. Rather, I see its primary purpose as increasing the player's maneuverability and offensive abilities. Because the move quickly decelerates, it is almost entirely useless in time attacks, unless the player is starting at a dead stop on top of a steep, long, descending slope. As SpiritCrusher already alluded to, the move is useful for overcoming slopes that would otherwise require a boost panel (although I can only remember one that fits this exact description, at the beginning of Hill Top, Act 2). Furthermore, the Super Spin Dash is required to / drastically reduces the difficulty of defeating certain enemies in Sonic 3 and Knuckles (Marble Garden's Togemane (the bouncy, spiky badnik) and Sandopolis's infamous Skorps come to mind). That's also why I don't like boost mode: In addition to providing instant and maintainable speed, it renders the player invincible and dangerous to all enemies, further overpowering the move.
(...You know, I think I'll write my senior thesis on this exact topic. Lord knows I have sufficient material. :D)
*Although, as I've mentioned before, I don't mind seeing the occasional boost panel as long as they're zone-specific gimmicks. For instance, in Sonic 2 boost panels are only effectively used in Chemical Plant Zone, which is entirely justifiable because the zone is built largely around speed anyway. Starlight Zone, Stardust Speedway, Hydrocity, Launch Base, and Flying Battery also employ boost panels in such a responsible manner.