I must say that I did dive into the iOS version of S&SASR with some pretty lofty expectations, seeing as how I had already played the Wii version. It met close to half of them. I'll start off by saying that this is like Mario Kart for iOS, but with sega characters.
But, even with all of this going for it, it still has some fatal flaws. It may be that I was running it on a 2nd Gen iPod touch, but it frequently crashes whenever I try to go into Grand Prix mode, and that's the way you unlock courses. So I'm stuck with 5 or 6 simple tracks.
Another complaint I have is the control schemes. While I like how the racer is always moving forward and I dont have to mash down the A button like in the DS version, I still prefer to be able to hold down the accelerate button. The tilt controls require you to jerk your iPod to turn a smooth turn and/or drift (which is harder than it should be) And the only control pad option they give you is a side-to-side only mini joystick (pictured above) which even worse than the tilt control.
Because of the mix of only being able to slow down by breaking and the bad turning controls, you frequently get stuck against edges of cliffs or walls. This said, the game that looks promising at first can quickly become annoying.
If you're looking for a Mario kart for iPod touch or iPhone, this is the best thing you can get without jailbreaking your iPod and getting a snes or n64 emulator (note- if you take this route, you MUST own the actual game cartridge of the rom you're downloading to make it at least partially legal otherwise it is illegal and you can get sued and/or put in jail.) I believe this is one of those "you get a little more than what you paid for" games, and it's only 1.99 USD.
It was worth my purchase due to multiplayer and the occasional grand Prix that it doesn't crash on. Now before you go deciding wether or not to buy it I recommend watching some gameplay videos ( rule of thumb: if the cuss word rate is more than 5 per minute, it is a game for patient/hardcore gamers and is too frustrating for beginners, noobs, and mediocre gamers) and reading some more reviews.