I'm a member of the MSDN Professional (for business reasons) and unless you have some specific need (e.g. developing drivers, hardware, software, etc.) I would caution you about subscribing to the MSDN service and installing 'beta' or 'pre-beta' software...
First off, as a beta tester you're shaking out the bugs in their programs and you're not getting paid for it, as a matter of fact you have to pay them to be part of MSDN! Although there are exist agreements with 'industry partners' that can gain access and have all the fees waived.
Secondly, the number of bugs, or as I've always called them 'undocumented features' in these betas would be enough to scare away most prople from even going anywhere near it... frankly I'm surprised at the bugs still in the final shipping versions... but that's why we have service packs!
On the other hand if you have a ligitimate need for access to the betas, you have to put up with all of this.
Bottom-line: There's nothing to be gained from the betas, wait for the official release version.