I recently sold my copy on eBay
I'd like to mention the load times are bad only on certain consoles: yes, they're long, but that video floating online is about 3x as long as my load times..
Second of all, the game is MUCH harder than Sonic Rush [DS] and Sonic Adventure [DC, Gamecube] and certainly much harder than the original Genesis games. If I sold it, that's because I spent an entire month playing it and didn't finish one story.
Now, I mostly play RPG's, rhythm games, and fighting games, so these action/platforming games aren't exactly what I'm used to, but the game borders on impossible: mind you, I beat Shinobi on PS2 [which is hard, most people hate because of it's difficulty]
The level where I failed to progress in Sonic's story was the running level between kingdom valley and the aquatic base, it's TOO fast and I always miss one jump and end up dying.
Otherwise, it's a good game: I'm actually going to rent it on PS3 and see if it's any "better", but I'll gladly buy the 360 version when it's $19.99, it has good music, great graphics, and it is a CHALLENGE.