I live Marvin, but I think he's criminally under or miss utilized in Corbin's 'system.' Get rid of Big Al, open the offense up, run plays for other players, such as Marvin, and I think he'll do much better.
The big mystery to me in all this is all the love Corbin's giving Foye. He's this year's Raja Bell. I wouldn't be sad if Foye were shipped off in a trade, but I would be disappointed if we gave up on Marvin so soon without giving him some kind of actual role in the offense, other than to pick up Big Al's leavings.