New Green Hill Zone demo which includes modern Sonic on October 18th
The blog says it'll be released a week later on PSN but on Twitter they clarified it was the 18th for both Xbox and PS3. At least in Europe.
...which is today. I should check the PSN.
Last time I played it was on Mega CD.
Aka a long, loooooooooooong time ago.
Slightly different trailer:
And when I play classic Sonic soon after playing Sonic 4 I keep hitting jump when I'm in the air because I got so used to using the homing thing to get forward momentum before landing.