I need to thank 3 different site for this info:
SpartanForce.com
HaloCouncil.com
halodestiny.com

In an article by halodestiny.com there are scans that show a newly released magazine with Halo articles and pics in it. Specifically there is a shot of purportedly playable Flood.

This revised mode of infection features:
12 person playlist-2 infected, 10 spartans
Infected have claws and enhanced vision

Now I don’t know about you, but I’m very happy to see this change. Instead of just a simple armor color change to denote you’re infected as has been in previous Halo titles, you now turn into a flood soldier. How sweet is that.

So now the question becomes, will there be specific animation for the first time you turn into Flood once you respawn? Wouldn’t that be cool!