Yes, the bits are finally here...
As announced today, Microsoft Certified and Gold Certified Partners with a SPA agreement in place and access to PartnerSource can now download Microsoft Dynamics NAV 5.0 W1 Beta.
You can choose to download the Marketing Beta VPC (includes Windows XP, 2007 Microsoft Office System) (2.8GB download) or just the install files.
The test starts now... 
IMPORTANT UPDATE: the password given by Microsoft for the VPC machine is wrong. It's not "pass@word" but "pass@word1". Enjoy.