I agree with shiela_robins with the need to be easily cleaned. Having a specially designed rack to be used in a dishwasher would be nice too. The other thing is they need to be durable. Most bags don't last long before they start splitting/tearing.
Personally, I've found that the inexpensive plastic storage containers work great. What I would really like is more options that are not plastic.
"No one gave us a guidebook for managing a planet. We're writing it ourselves now, from hard experience." - Earth by David Brin