Some things I like:
- Transitions between windows are super fast and smooth.
- Style is clean and lightweight. A distinctive approach.
Things that made me uncomfortable:
- No Start button (although you can download 3rd party programs to bring it back)
- Trying to have two windows next to one another felt much harder to accomplish. Using Snap! just felt way more complicated than what'd you normally do in Windows/OSX.
- Start-up screen is kind of overwhelming and inefficient. It's a cool concept but the variety of boxes just makes it hard to interpret information quickly. It reminds me of iGoogle. I just don't need all that information at once.
- Some of the features are hidden and require a lot of exploring to get it right, like remembering which corner does what when your mouse moves there. I've never found those type of mouse gestures intuitive.
But I should note that I've spent decades learning one paradigm so this could very well work with a younger generation that isn't as married to a UI concept.