I wouldn't bother...
Currently running it. Yes it is faster than Vista but not massively so. A few GUI tweaks seem to have done a job of making it feel quicker.
The UI is just bollox. There's now too many places to launch things from. Stuff like the enhancements in WMP have been virtually hidden away and can only be accessed if you're lucky enough to work out that you need to put it in mini player mode then press the playlist button and then there's an icon for it.
The taskbar is a fucking joke. Either you end up with a load of icons where the only way to tell the difference between a running app and a shortcut is the fact that one of them appears slightly raised, or you alter the option to show text for running apps and end up with a mish-mash of window switching tabs and shortcut icons all mixed up. Even worse is messenger if you use the show text as it no longer puts an icon in the system tray so you have a windows switcher button and if you click on it to show the contact list, you end up with two window switcher buttons for it. As for the system tray, we won't even go there.
People are raving about the power button on the menu. It's the same as Vista except it uses words instead of icons. Wow.
Aero peek. Has there ever been a more pointless thing to put in an OS?
People have commented on how much simpler the Networking Center is. Are they fucking blind? It is the most busy looking window of the lot. As for homegroup, it's broken. If you want to change the password, it'll tell you you need to be in a "Home" location even though the location says you are. So you delete it and go to recreate another only to be told you can't for the same reasons.
Yes I know it's BETA and to expect things but it has been widely bandied around as being feature complete, completely stable and ready for release etc when the truth is that it isn't anywhere near.
Good things? The Library feature is nice if a little confusing at first - stick with it. Err...err...err.....oh yeah, it's quite a stripped out OS - no mail, messenger, movie maker etc. There was something else....ah Device and Printer manager is a nice touch.
In short, it's not worth bothering with yet. Stick with Vista. I've used vlite to create a customised stripped out Vista installation and I swear it feels as quick as Win 7 does once you've got rid of the crap.