Volusion powers over 30,000 stores and has the basic features working well. It also offers a nice abandoned cart feature and if you need any extras, there's a decent app store available.
Volusion doesn't charge a transaction fee, but it does charge a bandwidth fee for all plans. This means that every visit to your website (including bots) will count towards your overall bandwidth, and it adds up fast, even with 2-3 pictures per product page. 1Gb bandwidth could mean 20-30 visitors per day, which is what the $15/month plan will get you. Additional bandwidth is $7/month, so even if the pricing plans seem accessible at first, this bandwidth limit can run up fast.
Volusion also doesn't offer SSL (secure pages that start with https) by default and will charge you for that, which most other providers will give you out of the box. This also can get quite costly ($49 to $990 per year).
Overall I feel like the usability and competitive features you get with Volusion are outweighed by the somewhat predatory pricing, which could catch the beginner entrepreneur by surprise.