You can run RAID with WHS. WHS will just see this as a single drive (though it is more difficult to set up). The advantage of WHS is that it takes single drives and manages them as a pool. Through the Connector software (or RDP) you can set up each of the shares you create to duplicate or not. Duplication makes WHS physically make a copy of anything in the share on another physical drive - i.e. it can be more efficient than RAID 1 or 5 which will duplicate all the data.
Example; I've about 4tb of DVDs copied to mine, but as I've got the original disks this folder isn't duplicated. Another folder with some DVDs I've created are duplicated as I wouldn't have the original DVDs as backup.
I've tried the W2K3 approach too, and I found it much more admin. Most of the admin/config is done through the WHS connector software on the client and is pretty easy to use.
I've not set up my PS3 - cos I don't need to - but it should work - it can certainly see the WHS, but I've not setup an account for the PS3. ATM I'm streaming everything, music, videos, DVDs, BD-DVD etc to Media Center PCs. WHS PP2 and PP3 have made it easier to share the media content across the network, especially in Media Player and Media Center.
I think MS have a 120 day trial of WHS if you go over to their connect website for WHS - but be warned it will wipe all your disks on install as it create the storage pool.
Hope that helps.