Commuting - Backpack or Arkel Bug

I'm a teacher and a dry days commuter. I have a Vaude Office bag pannier which until now has proven a beautiful buy.
However sometimes I need to go shopping or take extra stuff to school and I have been looking for an extra bag. I have read all the posts on Arkel Bug and I simply love it but it is a bit expensive.
I've also been looking at backpack with a mesh which keeps the back pack away from your back allowing for air to cool you down avoiding sweat. This sort of backpack I could also use for longer mountain bike exits. Has anyone tried this? Does it work? I don't want to arrive to my school with my back dripping sweat, I ride in my work clothes and that's rather uncomfortable.


Thanks

If you don't want the sweat, get the bug. It's not the most comfortable backpack but to go from parking lot to your office it should be ok.
Once you get it, you'll be ok with how much it cost. Very well made and should last you for years.
And you won't have the high center of gravity or weight of books on your back while riding.

I ride with a BP on mnt bikes to work. I don't mind a little sweat. The mesh backs help a lot. I ride with Deuter pack, made for biking. If you ride in the drops you probably won't like it as much. I recently started commuting on my touring bike and don't like the feel of the BP in the drops. It's OK on the top and hoods.