1. The guy who said 80% against CPU and 40% against HUM is pretty much dead on to how I use man coverage.
2. You don't need a great team, but you need to have comparable talent in the secondary to the opponent and a LB who is within 5 points of SPD of the opposing HB and TE. This speed difference determines how much I shade the HB/TE/FB and how often I can roam freely. The better the cornerbacks in the secondary, the better this works. It is nearly impossible to run man defense with bad cornerbacks and I wouldn't suggest that to anyone.
3. I'll always control a player with no assignment to begin with and I guess you can call it "floating" after the snap. Most times there is a specific route I'm trying to stop and that's my first task as the roaming defender, then I'll either move to a secondary assignment (HB/TE in the flats) or roam into another WR's route.
I've tried running man with West Virginia for example and it failed miserably because their talent in the secondary is atrocious. With Ohio State or Florida State, I'm usually able to make stops and force turnovers. Those are elite teams as examples, but you get the point. I'm using 67 OVR UNLV in my online dynasty and can force turnovers in man defense because I've recruited some great cornerbacks.
Anyways, sent you a friend request: McFlurry84. Should be playing an OD game in a few minutes, but we can play whenever we're both on.