The reviews are in for the beta of Ubuntu 11.04, also called Natty Narwhal and the reactions are mixed.

Reviewers mainly had qualms with the brand new Unity interface, which Mark Shuttleworth earlier said would bring the OS a superlative, more interactive look. But reviewers miss the GNOME interface, saying Unity is not ready for prime time.

Unity is a radical change from the traditional UI that made Ubuntu so popular. In Unity, the main toolbar remains on top, just like in Mac OS. An application launcher dock stretches down sideways. The icons are large, and 2D/3D interface is designed to ultimately take advantage of touchscreen capabilities.

The Register said Unity UI was much like the Mac OS X interface, but not as polished. Others noticed that the top dock is unusable, but could be used for other functions.

The app launch dock was useful for one click access to frequently used programs, but it did not offer much flexibility in customizations.

Overall, some said that Unity could ultimately trump GNOME. But that would be in a few years, not now. The interface is fast, but it offers no flexibility or customization for users to set up the desktop the way they like.

Bugs in applications such as LibreOffice and Banshee were also spotted by the Register. One commonly praised feature was the improvement to the SOftware Center, which looked better and had a ratings feature. The improvement in configuration features was also praised.

General thoughts? Hang on for beta 2, or wait for the final version, which should come out before the end of this month. But there was general agreement that this was a big gamble.

PC World earlier touted Natty Narwhal the best Ubuntu OS so far, with the interface and updated applications. But Unity has taken on a life of its own, and it could break or make the OS. That will be the main topic of conversation for this OS going forward.

There were also stray thoughts of remaining with GNOME desktop interface, for which version 3.0 was announced today. This was the first rework of the UI in close to a decade.