LBer is a huge issue for us. Shanle, Fowler, Fujita and in all probability Coleman are not starting material, and Singleton, if he's even here next year, is solid but replaceable. With Burnett still a question mark, that leaves only 2 bona fide quality LBs on the team in James and Ware.
For a team running a 3-4, that's a big honking alarm bell.
OT is obviously just as big a need, but Adams will at least be back on one side, and Pettitti should be better in his 2nd year. It needs to be addressed still, for sure, but personally I don't see it as important as a lack of LBers in a defense designed for LBers to make plays.
That being said I'm sure the O-line will get plenty of attention.
FS and K are both issues, but neither position will break the bank or be the reason that another player can't be signed. WR will probably be a mid-round draft pick this year, TO aside there isn't too much enticing out there that really provides a big upgrade for us (Randel El would be intriguing, but he's at best a #2 and is sending signals he wants Reggie Wayne $$$).
Note, this is not an argument to go get Arrington, who IMO will be too big a gamble to justify his price tag, just noting that I think getting at least 2 quality LBers through FA or the draft is imperative here.