Great topic -- I'm in a few of these leagues, so I'll discuss my strategy in a nutshell:
The biggest difference I've noticed is that mid round RBs are there a lot later than they should be. With that in mind, I usually draft 1 RB in the first two rounds depending on value, then take 2 WRs and a QB in the next three rounds, followed up by several high upside RBs later. An example of a few of these drafts in 12 team PPR leagues to give you an idea of what I'm looking at:
1 QB, 2 RB, 3 WR, RB/WR, TE PPR
A. Rodgers, E. Manning
D. McFadden, M.Ingram, T. Hightower, M. Tolbert, M. Barber
M. Austin, M. Williams (TB), B. Lloyd, B. Edwards, A. Roberts, D. Moore
J. Finley, R. Gronkowski
1 QB, 2 RB, 3 WR, RB/WR, TE PPR
T. Romo, S. Bradford
S. Jackson, B. Wells, M. Lynch, J. Starks, W. McGahee, D. Carter
A. Johnson, M. Austin, B. Lloyd, M. Thomas, M. Sims-Walker, D. Moore
R. Gronkowski
Again, my RB2 position is pretty up in the air, but there are a lot of guys who could potentially fill that spot for me. I'm confident that between them and my waiver picks I can find a #2 RB, and I feel like I'm coming out of these drafts with three top 20 WRs and a top 5 QB.