Thanks for the note. We've done this in the past, but sometimes the folks at the ticket desk won't allow it if they deem the dog too tall ("I'm sorry, sir, but she can't stand up fully, her head is touching the top of the carrier."
Me: "So? You don't have any problems jamming me in a seat where I can't stand up or straighten my legs, either!")
I talked to a lady who regularly flies with a little Yorkie under the seat, she says other passengers sometimes give her looks or even comment about objecting to having to ride with the dog in the cabin. I'm sure some folks are allergic to them, but as far as hygiene goes, I've flown next to plenty of people who were far more objectionable than a clean, well-groomed dog.