MarketPress Feature Request

When I am on the product item page, there is no way to get to any other category directly without going back to the products page - that is very tiresome.

Looking to add the above feature in the main Navigation bar, however shortcode doesn't seem how fit the requirements. Would like to have a inbuilt feature to add such option in the Main Navigation.

Also another important feature request for coupons:
1. There needs to be an option for minimum purchase - you don't want someone purchasing a $2 product and using a coupon
2. There needs to be an option of one use per customer.