Has anyone here had the experience flying commercially on an airplane carrying a drone? I own a P3S and thinking of bringing it on vacation but I'm unsure about the legal or security issues.

People fly with their Phantoms every day.
You just have to make sure that your batteries are in your carry-on luggage.
Search your airline's website for their policy on lithium batteries.

I concur with labroides.

I read somewhere that Alaska airlines won't allow carry-on OR checked.

Definitely check the carrier policies....and don't try to sneak it on.