I gave my girlfriend my old Performance rack trunk a few months ago. She's liked it, but it'll soon be too small to hold all her stuff. She's starting grad school and will have to carry around a bunch of books and binders both on and off the bike.

I was thinking of getting her the Nashbar Backpack/Pannier hybrid.

On the other hand, I don't think she'd like having all that much weight off-balance on one side of the bike.

What about the Nashbar daytrekker panniers? Are they big enough for books and binders? I like that they can be pulled off the bike and carried around as one unit.

Any other recommendations? There doesn't seem to be a lot of variation in commuting-oriented panniers, having looked at a few online stores... A pair of panniers that can be removed from the bike as one unit would be really nice, as would a shoulder strap.