I've been enjoying mine for a while now so here's my more extended view on the little big beauty (for a picture click here):
"I went with the front adjustable strap which I definitely prefer to a side one, like the one on my crumpler bag, as it's much easier to yank on the strap and pull it into position with one hand and is a lot more adjustable in terms of getting it to sit right. Also, you've got all the fastenings within reach so it's much easier to micro-adjust while riding and without having to reach round behind you. Plus in theory you can switch which shoulder it goes over, although I've yet to try this (force of habit I think).
It's surprisingly light on the back when positioned right. When it's only got a few things in I barely notice it. I probably should make more of an effort to use the compression straps as sometimes it does feel a bit "floaty" when near empty if if don't compress it down, although this might be because I havn't fully broken it in yet. It generally "wraps" very nicely as it gets emptier.
Visibility: there's only one area where it interferes and that's when it's very full and then only slightly in the space right behind my right shoulder, so at the limit of my perpheral vision and where someone shouldn't really be riding except in a race (but you know London commuters, they usually do).
The larger of the two zip pockets on the exterior comfortably takes my abus cable lock (I think it's one of the 80cm ones) and leash and I can get all my tools and tubes in the smaller one so they don't grubby up the inside."
