Speaking from a buyer and a sellers stand point there are both positives and negatives to redbubble.
Positives - Simple to use.
Simple to contact sellers.
Original designs, bespoke and
A great platform for creatives.
Negatives - Work is prone to be copied
without permission unless
Pricing can be high, with
added costs given for the
Maintenance of the site.
Despite the negatives, I do like using Redbubble, and I do reccomend it to others.