We have 3 sets of these and are happy with them. They are large enough for a daily commute and are holding up ok. I had a seam come apart on mine when I really overstuffed it, but a quick repair with a sewing mackine and they are as good as new.
Nashbar ATB Panniers
Edit-specs:
weight------------ 1302g by tech
materials--------- nylon cordura
dimensions-------- 14" x 14.5" x 5.5"
volume------------ 2350 CU. IN.
attaches/support-- attaches to rear rack
waterproof-------- water resistant
features---------- 1 main pocket, 1 pocket on flap and 1 on side