While the the best of them offer surprising amounts of flexibility, they also impose stringent enough restrictions to page design that you shouldn't be able to create a really bad looking site using one of these services. Typically you can get a Mysite.servicename.com style-url with no commerce abilities for free from one of these services; you have to pay extra for a better URL and the ability to sell. One issue to consider is that if you eventually outgrow one of these services, it can be hard to export your site to a full scale advanced web hosting like Dreamhost or Hostgator. If you know that's where you are eventually going, it may be better to skip the sitebuilder step.
Most of the products here can tell you about your site traffic, though the amount of detail varies greatly among them, and it's often tied to premium account levels. For example, Weebly can not only show you page views and unique visitors for each day of the month, but also search terms used to get to the site, referring sites, and top-visited pages. Wix and uKit, at the other end, have nothing in the way of built-in site stats, instead requiring you to create your own Google Analytics account, and even that requires a paid account. Another drawback of that approach is that you can only see traffic from the preceding day and earlier; it's not up-to-the-minute, or even the hour.
I have an online store on eBay and sell collectible postage stamps from all parts of the world. Their auction site is awesome but their fees are becoming outrageous. When you add that to the fees from PayPal, I’m not sure who I am really working for. First of all, is there an auction house plugin that resembles eBay what you recommend. And secondly, what is the minimum amount of memory my computer should have? I would have about 250 listings at any one time that would last 7-10 days.