I installed this plugin on my site and found it pretty easy to use. I like the fact that they provide video instruction for set up and use. I have had no problems with the checkout system, and it has notified me of every sale via email. I find that the layout for the free version is limited, but after all it is free. There are charges when a sale is made, but in comparison to websites like ebay, the charges are pretty minimal.
The full version is a bit pricey, and I think I would purchase something with a one time charge before I would sign up for the monthly fee. As I grow my business, I will probably look for something with more features. One feature I would like to see is offering price breaks for a volume purchase ie, purchase 1-20 items xyz price, purchase 21-39 items =xyz price ect.
Overall, I would recommend this plugin as a good starting point.