Just poking around market press for the 1st time and found something a little quirky.
The visual editor wasn't working (html editor was fine) and neither was the upload file button. (Both in the Create New Product screen).
Didn't have any product category or product tags so I thought I'd check if creating an entry for those would solve the problem.
Apparently it did (but maybe it's a coincidence).
I didn't notice anywhere in the setup instructions that you had to create a category before a product. If you do then it would be good to update the instructions.
This is just for your information.