I"ve experienced the opposite with my MBP - i'm sitting here with FULL signal. In my room, the same room that with my iBook and Sony with External Wireless I got ZERO signal. Maybe 1 bar if I was luck and held the computer
"just right".
The Signal Strength with the Airport Extreme N router is about 2 bars stronger when you open the signal meter do-hicky. But overall, i'm impressed with the reception.
Worth noting, my router is in what used to be the garage in my house, some tight angles with lots of metal studs between me and it. We aren't sure how much metal we have in our walls - but enough that it interfered with the wireless (and cordless phone).
I did see a strength change from about 85-90% to 100% by switching from the Belkin N1 to the Apple last weekend. Overall, i'm pleased with the Apple.
I don't take my computer places - so i can't comment on the connections out and about.