5 pages of people whining that there is a watermark on beta builds. The funniest ones are when they threaten to stop helping Microsoft test their software unless the watermark "issue" is fixed.
It's real simple, the watermark is there so that people know they aren't running a stable build. If that is bothering you go back to the stable build. The chances of Microsoft removing it are slim to none., no matter how many people complain.
The point of beta and dev builds are to let people test out features before the next stable release is released. You also agree to the possibility there may, and most likely will, be bugs in the software. To complain that the software isn't up to your standards because there is a small watermark on the desktop is pretty asinine.
The watermark is a minor annoyance, you can make it so it's hidden by the taskbar, you just have to set it auto-hide.