Outside of running back the Bills need help at every position on offense. They basically played a team of backups and third stringers this year, with predictable results. The interior offensive line isn't horrible, but they desperately need help at tackle. That'd be my top priority for the offseason, get a true starter at offensive tackle. They've been trying to fill that spot with backups from free agency or fucking undrafted rookies and it's just been a train wreck.
On defense they need help at defensive end pretty bad. Opposing teams could just run off tackle all day long and the Bills couldn't do a thing about it. The Bills are so small on the front seven they just get pushed around and pretty much can't stop the run without blitzing. Maybe Merriman will help if he ever gets healthy, but I have my doubts of that.
The secondary is in fairly good shape, but then since the Bills couldn't stop the run other teams didn't really have to pass that much so it's hard to say. The cornerback situation seems pretty solid when they're healthy but I'd like to see some improvement at safety.
Special teams are about the only thing the Bills seem to have locked up. Good kicker, great punter and return men out the ass.
As usual this time of year I have to wonder if the Bills have anyone competant running the scouting department, looking at the past ten plus years of drafting. I'm not optimistic.