i have the vertex 200aw myself, and it does get heavy (obviously not as heavy as a fully loaded 300), but the strap/suspension system is excellent and i can walk around all day fully loaded...i did fly on some smaller regional jets recently and my 200 was gate checked on nearly all those flights...on the sole flight they let me carry on it did fit in the overhead (crj 700) but it took some work...
i also have a fastpack 250, which puts the laptop right against your back, and its much less comfortable...after a short while it feels like you've got a board strapped to your back...and that's probably not very good for having the screen press down on the keyboard either, assuming you don't have a protective pad between...