m0dus, it's an awesome and funny theme. I like the choice of the Eggman "block list" icon.
Played through a game (Bad Future, I need to practice some of those later special stage again), then played through a little bit with Tails. All sorts of new sprites were drawn or edited for him, including dropping down the Palmtree Panic vertical loops the wrong way, which is awesome. Special stage sprite looked a little off, but those sprites always looked odd anyway.
It's really impossible to begin to describe the care and attention that went into this game. I keep noticing little aspects I forgot were in Sonic CD, but here they are accurately reproduced. The game handles excellently, with the only weirdness being able to launch Tails into the stratosphere when I started flying coming out of a vertical tube (it seriously took him about 15-20 seconds to come back on-screen), and I thought I noticed more of a tendency toward crush deaths, even when the cylinder was rising up, but then I remembered those plaguing me in Sonic CD to begin with, so can't fault him for being accurate.
Sonic CD isn't my favorite Sonic game to begin with, it's alright, but the level design is just all over the place, and by the end starts getting a little Dimps-ish with the spikes and "gotcha" traps, and there's tricks to time traveling in limited areas that aren't obvious and aren't explained to you, so you could carry a Past sign through a major portion of Metallic Madness and have no idea where you're supposed to get a run up. And the stages are filled with all sorts of useless little alcoves and dead ends with nothing inside, that may have some meaning in another time period, or may not. It looks great, and it still plays pretty well, so don't let my opinion discourage anyone looking to buy it, and honestly at $5 for the best presentation an iconic Sonic game has ever had, you can afford the gamble.
One small disappointment that I had was that the intro and ending still ran in sort of broken Gems speed. The main intro runs just a little too fast, and the Ending is WAY too slowed down. I guess Sega was trying to match the music back in Gems, and Taxman couldn't really touch the video mastering, but it was a little disappointing that it wasn't running smoothly. Maybe it had something to do with the Japanese version having sound effects overlayed over it?
Edit: Clarification, I realize the original Sega CD version ending ran at choppy-mc-slow framerate, but it's clear the video was drawn to animate faster than that. The parts when it "boxes in" on the other hand play a little too fast, like they did in Gems. Again, I don't blame Taxman for this.