Heh, don't worry about bag limits - it's all just social engineering.
Virgin America, Washington Dulles to Los Angeles:
0) One big-ass duffel filled with clothes, checked.
1) One traditional carry-on sized suitcase, filled with clothes.
2) One CamelBak back-pack, filled with a) Tablet PC in case and b) assorted other things (Hudson News for example).
3) One LowePro camera bag I bought at Ritz Camera, containing a D80 and 2 lenses.
4) One set of 055XPROB legs in the plastic bag they were shipped in.
A total of 4 items, absolutely no problems, not stopped by TSA, flight attendants, or anyone. Granted, I'm 18 and I don't think anyone's scared of me or anything but so long as you don't take either a huge, obviously too-big-for-the-overhead-bin bag or 2 carry-on suitcases nobody cares, just like nobody cares if you bring a carry-on suitcase, a purse, and a newspaper and a few magazines in a plastic shopping bag twice as big as that purse.
Keep in mind, this is the same TSA that missed the 3 liters of water that I accidentally left in my CamelBak, and this was with the drinking tube hanging outside the backpack.