I am very impressed with what I've seen so far. It is a very great OS with a superior UI. After using it for a day or two I have to say the UI is a lot nicer than its competitors and it manages to keep things interesting with live tiles.Therer a few minor things that aren't available yet but that is to be expected from a new OS.The drawbacks I would have to say the marketplace, it feels like there are only a few great useful apps and the rest is just so they could say we have more than 35,000 apps in the marketplace. There should be a little bit more quality control. Another drawback would be that not a lot of people own a WP7 yet so it feels lonely but I guess Xbox users can make up a bit for that.It has a lot of potential, I just hope Microsoft keeps improving it and hopefully more developers will get interested in developing quality apps.