This is still in an experimental stage but the potential is exciting. We have several websites but never turned them into commercial sites (sites that actually sell items) because we would have to buy add-ons or buy new packages.
If this Google gadget works as they project and if it stays free (IF) it could get many of us into our own commercial site without having to rely on other selling sites (eBay, OLA, Bonanzle, etc).
While a successful launch will affect the other sites to an extent, I don't believe it will be the end answer for everyone because just having a selling site does not guarantee sales. Your site must be advertised and marketed like anything else. The other selling sites have done a LOT of marketing to get their market position, but if you use them wisely, you can help your personal sites as well.
eBay will not allow you to directly link to another selling site, while some of the others will. You can still use all of them to help promote, while selling through their site as well.
I have not looked at it closely yet, but you can bet I will and quickly. Most of our items are in Excel documents and it looks like we can upload those with minimal effort. WOW! What a time saver! And did I mention that it is FREE?
As I learn more, I will share it, but for those who already know more, PLEASE share it with us.