Here's the short version: I love it, you should buy one.
Here's the long version:
Got my new Kriega R25 backpack in the mail a couple of nights ago. So I rode the long way to work yesterday to get in a short test of how it works.
I ordered it from Aerostich for $135 last Friday. I got the backpack itself ($117), and a latch on front pack ($15) to put my camera in.
The pack is nearly perfect, but there are two major faults that I have with it. Just to be fair, I knew about both of them, so I can't really complain.
The first one is that it's not hydration bladder compatible. Not really that big of a deal, but when it's hot, I like to take my Camelback along for some water.
Secondly it's not 100% waterproof. They tell you this upfront, so it's not really a secret you'll find out when your stuff is soaking wet. They do say it'll hold up just fine in light rain and such, but since it is stitched together, eventually water will get in. That's why I bought the separate pack to attach, because it comes with a 100% waterproof cover. I don't mind if my hat or what ever I've got in my pack gets a little damp, but that's a big no no for the camera. Kriega does offer an optional inner bag that is sealed from water and maybe if I tour much with the bag I'll pick one up. Along those lines, the R35 comes with the waterproof inner bag.
Speaking of the R35...I didn't get it because I was afraid it would be too big. The R25 is a good size pack IMO for the majority of the time. I'm guessing I could easily fit a weeks worth of [motorcycle] travel clothes inside of it.
The harness system makes it look like a parachute, but it does its job and keeps everything in place. There is absolutely no movement of the bag when you have it on. I hit the highway for a few quick blasts this morning and the only observation I have about the bag is that I didn't even notice it was there.
Build quality is about 100x better than anything you'd get at the local supermart. Thoughtful clips are where they need to be to keep any left over straps in place and the adjustment system is perfect. There are 4 metal O-rings that you simply pull to fit the pack to yourself. Also the shoulder and side straps are designed in a way that makes it very easy to put on, even over a leather-riding jacket.
Basically if you are looking for a really good quality rucksack that you can use everyday for years to come, I don't think you'll find a better one. The features and unique harness make it the best motorcycling backpack you can buy.
$117 at Aerostich
$15 at Aerostich