There are some who do it, but I couldn't see trying to ride the trails with panniers. Just too big, low and wide and they would get tore up by vegatation, rock gardens or tree crossings. Plus, with everything on the bike, the bike would handle too poorly. The one downside of the seat pack is you can't get off the back and down (back yes, just not down) when doing steep technical terrain. Just have to adjust to it or walk a section if it seems to scary. It does make it something of a different game when you're trying to ride with all the gear.

Big? It's only a 1800ci Osprey Talon 33. Guess it seems big when you're used to riding without anything on your back. Half the size of the Aether 60 I had been using for backpacking.

I actually bought the pack to use for light backpacking and figured I'd give the bikepacking a shot and see how it worked for it too. Works great, and not too much weight in it. I carry my kitchen, food, misc clothes and other stuff and my sleeping pad, which I just fold into a big block to use up space.

There is still extra room in the seat and frame bags and I hope to get things to where I can just have a 6-700ci, 10 liter pack, like the Talon 11, on my back. Minus the sleeping pad, I can almost cram everything in to my Camelbak HAWG (smaller 2000 model). Not much of anything I can drop, but I know it will work if I just relocate a few things to the bike packs.