As it's been repeated over and over, you can preorder the PC version for just about $20 right now if you get it from Green Man Gaming, or if you wait until it's announced for Steam, you can get a bunch of free Sega Steam games for under $30.
Otherwise, console version, we're not going to know for probably another week or two about any launch time sales. Watching Amazon is your best bet.
0:14 Green Hill
0:33 Chemical Plant
1:08 Sky Sanctuary
1:47 Speed Highway
2:29 City Escape
3:38 Seaside Hill
4:33 Crisis City
5:22 Rooftop Run
6:20 Planet Wisp
7:01﻿ Soinic 1 theme
So that was the Classic version of Crisis City in the Modern Era trailer! MMMMM, that Planet Wisp...
EDIT: Looks like in the Extra Missions you can
call certain characters from the game to help you, essentially just as powerups and not actually playable (Taken from Sonic Retro):
In levels with Tails, you press the Y button to call him to you, similar to how the elemental shields were shown with Y in that one screenshot. Its likely all those little powerup icons we saw are things you can use with Y.
You can call Espio in a fashion similar to Tails. He has a grappling hook.
Theres also the ability to call Vector. He throws you to locations.
A team-up mission with Amy is included; she gives you the hammer jump.
Theres a team-up mission with Cream in a level with no rings. The only way to get rings is to call on Cream to throw you some.
Theres a treasure hunt for buried metals. You call Knuckles, who digs into the the ground for you.
Rouge team-up: heavily armored robots block youcall on Rouge to take them out.
Blaze team-up: the level has walls of flame which Blaze can extinguish.
Charmy team-up: he can make a vortex at your feet. What?
So I've been playing the PC version and apart from something odd in Chemical Plant Act 1, the game runs pretty well. I'm running a AMD 5770 graphics card, and after setting shadows to low and disabling AA, it runs pretty well.
The keyboard controls, though... I get the feeling that Sega just let an actual hedgehog walk across the keys when they assigned those. Plus you can't assign anything to Shift, Control or Alt either. Ah, well, I bought an Xbox 360 controller, I've got enough consle-ish PC games to warrant a proper console controller now. The game plays so much better with a controller.
EDIT: Ah, darn it. Wrong thread. I thought this was the OT.