I've finally ditched Windows 7 for Ubuntu 11.04, as Unity seems mature enough for my needs. There is however one little point of improvement: as a netbook user with a 1024x600 resolution, I see that most application dialogs are thinking they're still in 1024x768, ans many of them can't be resized, and when maximized, half of the dialog is shown and it's not possible to scroll up/down to see the rest, which can impair the usage.
Other than that, kudos to the interface team; Unity looks innovative, has taken the best of some UIs while developing its own rules (such as cleverly auto-hiding the dock to gain full width, which was a much needed feature). Something I also liked & found quite useful was the Mac Expose-like feature when clicking on open application icons.
If there was an Ubuntu release convincing enough to ditch Windows, I'd say Natty was it. Congratulations!