I wasn't that high on Coleman from the beginning, even after Week 1 when people seemed to be sold on him as the long-term answer. I'm pretty sure I said as much multiple times, but I won't go out of my way to prove it.
The truth, however, is in the numbers. We were using Mike Rob on approximately 30% of the snaps last season. Coleman's usage has dropped to around 10-20% over the last few weeks. We're using him about as much as we're using Kellen Davis right now. Marshawn's YPC is also down around 4.1; it was 5.0 last season. Admittedly, his 2012 numbers got a boost in the last quarter of 2012 when we were devastating teams with the read-option that no one seemed prepared for.
With all that said, I don't necessarily expect our run game to explode just because Mike Rob is back. I wish he had been healthy at the start of the season, so he'd be on the same page with everyone in terms of scheme and conditioning. Right now, I'm mostly expecting things to stay fairly level on that front (no appreciable drop-off or gain from Coleman-to-MRob). It's definitely good that we have him, though. I'm one who believes the I-formation is an important part of the overall offense even if the gains from those plays seem relatively minimal. The impact of those plays shows up at the end of the game.