MarketPress is great, but there are a few tweaks that would be nice:
In variations of a product there is no way to have weight be a variation. Because of this, you must create separate pages for each product that is identical except for weight.
If the client is selling gates, and they come in both white and black, they can be on one page with the second color be the variation.
However, if a client sells a product whose only variation" affects weight (thus shipping) a separate page must be made. Example:
A client sells a product named "Dogzymes Probiotic Powder" and it comes in 8 oz, 1 pound, 2 pound, 5 pound, 10 pound, and 20 pound.
As MarketPress is currently, that is 6 product pages that must be created to sell a single product whose only difference is weight.
An upgrade that included weight as a variation would be VERY good.