Just a warning, but the console releases of All Star Racing Transformed has proven some...interesting spoilers. You have to go out of your way to find them, but if you are interested in not finding them out, just avoid any Sonic/Sega orientated places. I have had a look and for the most part, they're thoroughly excellent. PC version looks like it may have the best secret characters through sheer audacity alone. Character spoilers: Team Fortress 2 vehicle and...Shogun: Total War?! Super Secret character spoiler for final unlock (?) that you may want to completely blank out on: SEGA! Play as the Daytona car on road, Afterburner Jet in the air and A BLOODY DREAMCAST CONTROLLER IN THE WATER!It's beautiful. To top it off, transformations are occasionally accompanied with the classic "Seeeee-gaaaaa" or the Saturn's "SEGA!" shout. Music that I've heard from the clips as well seems to be nothing short of fantastic. It looks and looks-like-it-plays like a properly fun arcade game.
In actually getting it, that remains up in the air. Still no PC release date, but I checked Amazon and Play and both have it down for £21 too (this is £4 cheaper than the console releases too, apart from the WiiU due to New Console Tax). No idea if this will be retail or digital or both.
All in all, it's looking like a very fun game, probably worth the initial asking price too.
I also found this. It's a bit different, but still enjoyable. I hope you like Sonic 2 music. (And if you don't, you're wrong!)