OL:
I'm fine with the LT position and the rest of the OL (when Butler is back). The Bills are 3-4 but not likely going anywhere so the off-season will be important for the OL to get stronger and better.
QB:
This is all about the coaching staff. Even though IMO the Bills QB have plenty of time to complete passes, both QB's are erratic.
We have plenty of competent WR's (Evans, Reed, T.O.) and some up-and-coming talent like Johnson and Hardy. I think one of the things that holds the Bills offense back is the TE position. Nelson is a step in the right direction, but the rest of the crop are not NFL caliber TE's, not for starters at least. The Bills do not have a #1 TE on the roster right now and haven't in YEARS.
My suggestion:
Keep Edwards and have him compete to be the #1. Fitz stays for the rest of his contract as a backup. I think Brady Quinn would be a good option (maybe a 4th round pick?, that I would gladly spend). Spend the early draft picks instead on LB and DT/DE and sign an experienced TE to compete with Nelson.
Oh, yeah and none of this works unless you REPLACE THE COACHING STAFF!!!!