I've also had a look at one in person at Henry's Toronto, and I'm looking or an excuse to get one -- although I'm not sure where it fits in with my needs.
I thought it looked quite a bit bigger than the 5xb. But I guess it isn't. It's a very nice looking bag, and light for a Think Tank. I do like the zippered pockets for keeping money, or a passport in.
Currently, I'm using a Saffrotto Domke 803 knock-off for going to work and back, because (unlike the Domke) I can carry my airbook and my camera. The retro's too short to duplicate that function.
When I'm not carrying the airbook, I tend to go with the 5XB or the small Barebones; around the city lately, mostly the barebones. So the retro would have to be an addition to one of those (with me there's never a replacement, just additons🙂 ) It might be nice bag to travel with; on my last trip, to Austin for SXSW, I took the Safrotto as a carryon, and then switched to the 5xb when I got there, because I wasn't carrying the Mac everywhere. The zippered pockets on the Think Tank are a nice touch, and are better than the pockets on the 5xb or BB.
But I don't really need it🙂