I just flew with Buddy a few weeks ago, and I agree with all of the wise people above. People did notice that I had him, and he barked at some noises on the plane. They let me preboard with him both ways, but on the way back they said that it didn't count as a pre-board. Screw them, I paid $100 ($50 each way) for him to fly on Jet Blue and I say: Pre board!
I used a Sherpa soft carrier - the "Backpack" which I love (and Buddy seems to love as well) He did fine - and a little hint to bring potty pads and use the "baby changing room" to potty him! Maybe it's not allowed, but no one yelled at me, and there was plenty of room, and a sink - and nobody else around to distract him from his "business"
Also, I used an herbal "calming treat" for him, which seemed to work well.