I'm in the middle of this process myself. Started out with e-commerce by Get Shopped. Paid for the Gold Cart plugin. Adding products and setting up was pretty easy BUT styling the pages is nearly impossible for a non-technician. I currently have 5 postings on the forum that have no comments. Clearly the weakness of that solution is styling and ton's of issues around image handling.
Then I tested eshop on my local host. I dismissed it because of the product entry methodology but to be honest, am not sure I gave it a proper testing and need to revisit. If I recall correctly, I needed to create a page for each product. [I cannot clearly recall if this my reasoning for rejecting eShop. I will re-test to give it a fair shake.]
I then purchased Shopp. The layout is clean, product pages and grid are straight forward but there is a java conflict that is keeping me from getting it fully installed. I have had some feedback from their forum and I DO NOT want to pay for higher level support. Hopefully I can get it installed for a full trial. If not, I'll be asking for my $$$$ back.
MY CRITERIA: Our retail store is a small boutique. The owners don't want to pay me [their semi-technical friend] to maintain content including product addition. We want a clean, simple grid display and an even cleaner product page. We need the sidebar widget's for the grid and product pages to be ONLY store related (ironically I couldn't do this with e-commerce as the widget control for the product page was hidden somewhere deep in a css and I couldn't find it.) I need the store owners to easily add new products and have Images come in without corruption (cropping). We also use NextGen gallery on our hope page and in the blogs so can't have a conflict there either.
Will report back when I find a solution that works.
Final note. I know you get what you pay for. I don't expect to have everything for free and will pay for a plugin if it's solid. What I really want is a good clean store at a reasonable price.