It appears that the search logic will return results if the search string matches the name or part of the name of an application. Searching for “firefox,” for example, will return the Firefox browser. However, if the search string is “browser,” the search result will not include Firefox.
This pre-stable release ships with Firefox 4 beta. By default, the tab bar on Firefox 4 is atop the address (URL or location) bar, rather than below it. Also the Reload and Stop buttons are now to the right of the address bar, which I find slightly uncomfortable. Having all the icons on the same side of the address bar, I think, is a lot more convenient than splitting their positions. Luckily, you can move the icons to any part of the address bar that you feel most comfortable with.
The Software Center in the last stable release had just one fee-based application. So far, there is none in this alpha release.
There is still more than four months left and several more pre-stable releases left, so it be foolish to make any final statements about Unity on Ubuntu desktop. Despite that, I still find Unity to be less user-friendly than the KDE Plasma Netbook interface.
Bug Report: For the features implemented in this alpha release, there were not a whole lot of bugs to report, on the two computers that I tested it on. The only major bug I observed was that the desktop will only display properly at the highest resolution of the monitors I used for testing. One had a maximum resolution of 1920×1080, and the other 1396×968. At resolutions lower than the maximum, the desktop displayed on a centered section of the available space, with significant dark sections on all sides, especially to the left and right. I am sure there are many more bugs, but that is the only one that has not been reported elsewhere.
Resources: Download an installation image here. Development notes and known issues about this release are available from the same link.