I travel frequently with my company laptop. Its a Dell so if it can handle it, so can your MBP Anyways, they will ask you to take it out of the bag, but I have not been asked to boot it up since last summer as they usually use the "magic wand" over the laptop ("sniffs" for explosives/chemicals). But, this will depend on the airport.
Just please remember, even though you make it through security, laptops, bags and other gadgets still go "missing" in the secured areas. So, keep a close eye on your laptop.
I went through this process 3 weeks ago. Make sure you remove your laptop from your bag. Better if you turn your computer off completely, as they open the lid to check for bomb material (you know, the little piece of cloth that they analyze). Process takes less than a minute, you won't be bothered.
My MBP and iPod have been all over the globe with me. SFO -> KEF -> CDG -> LHR -> OAK -> LAS over the course of 3 weeks and it handled itself like a beauty. A word of advice however; Apple products are like magnets for theft, even in airports and even on the plane. Going through security will be simple, fast, and secure compared to the greater threat of someone walking off with it.
Back up before you go anyway. Keeping the laptop accessible from your carry on baggage makes everything go quicker. Keep your eyes on your stuff at all times, and NEVER pack it in checked luggage.
Coincidentally, the only data I've lost through a X-Ray scanner were photos still on a compact flash card. It could have very well been the card freaking out as they sometimes do, but it did go through 2 or 3 scanners and about half the photos were garbage.