What are the problems with an LLC as a professional?

[brazilio]

Since taxes for most of us are done for last year, I got to thinking about becoming an LLC again when I file my poker taxes for the next year. I currently am a part-owner in a construction LLC that does mostly federal contracting. The actual LLC creation was relatively simple, although I was present and paying attention to only parts of it. Deduction-wise vs filing as a pro there have to be significant advantages.

A few months ago a guy in here asked a similar question, and if I remember correctly a CPA-type said it was improbable that the IRS would allow it, or it would be an audit-magnet for the business deductions you'd naturally try to take.
I don't remember the exact details of the reasoning why it would be a good or bad idea.

Anybody?