EA Sports MMA's free demo will arrive on September 28 for both Xbox 360 and PS3; you'll get four fighters, four different skill levels and a tutorial.
Further, as EA Sports has done with demos for NCAA Football 11 and Madden NFL 11, sending a note to someone in your friends list suggesting they try the demo will unlock free content in the full game. In this case you'll get "classic" Randy Couture as a playable character. (The current Randy Couture is already on the roster.)
The fighters you get in the demo are heavyweights Alistair Overeem (the current Strikeforce champion) and Bobby Lashley, and middleweights Jason "Mayhem" Miller and Jake Shields. Real-life referee Big John McCarthy makes an appearance; Jimmy Lennon Jr handles the fighter introductions.
The two playable modes will be a "Fight Now" bout set at HP Pavilion in San Jose, or an interactive tutorial featuring Shields vs Miller at the Horizon Center in Japan.
The full game hits shelves mid-October.