Drive Extender has been removed, and we dont even have word of how WHS will handle multiple hard drives. You will most likely lose everything in your BETA when RTM comes out, even despite DE's status. If you feel that attached to WHS, go with v1 for now, but keep an eye out for what MS plans to do with the WHS line. Otherwise, start looking for alternatives like 2008 R2, Linux RAID, ZFS, or some other storage solution.
I heard WHS Vail was making raid the preferred solution, Because the servers will mainly be sold by Dell/HP etc they will setup the raid, but this will make it hard for many people to upgrade. I got my stuff already all on RAID so it doesn't bother me, other than beta expired and i had to go thru a few hoops to get it to last a few months longer.