I had a long search for my perfect everyday bag. Imago, Cafe Bag, Zephyr, Red Oxx Gator, a bunch of others. I preordered the first generation 13" Ristretto in olive and cayenne (back in January 2008 when it was $70!) and it was my perfect bag. Used every day until I upgraded to the G3 last month. Actually wore out the buckle (TB sent a free replacement of course). I rarely carry a 13" laptop but for the past year I have carried an iPad. I like the structure of the internal computer sleeve.
Anyway, the G3 is my more-perfect bag. Didn't think I'd like the steel-iberian combo but I do. The new sealed zipper pouch is great. The poron grab handle is a significant upgrade. I like the curved absolute shoulder strap but that's nothing new for most folks. The ballistic nylon is an improvement in that the stiffer structure keeps my little pouches of stuff from tugging the upper lip of the main compartment down.
There's only one thing I miss, though, and that's why I'm writing this review. I really miss the internal flat zippered pouch. It was perfect for my passport and checkbooks. The organizer pouches really don't do the job as well. Tom: for the G4 if you could re-introduce some sort of integrated flat zippered pouch, that would be nice. Could be very simple, like the ones in your old cordura shopping bags (I miss those!), or bigger like the old Ristretto. But the new zippered pouch is not great for this -- having important small flat items just rattling around loose. And the organizer pouch (I use one for my iTouch and another for business cards) is a bit awkward for the purpose.
So that's my take -- a great bag but for me with one tweak's worth of improvement to go.