There are scattered posts here and there, but I thought I'd make an all in one.
1) if you upgrade or install 8 from fresh, you must babysit the R3 (and maybe other models as well) unless they are CERTIFIED Win 8. If you don't babysit, every time the install program (or once you get it installed), does a warm reboot, the system will hang part way through the boot process. This can corrupt files, and/or the file system. If you use software (Windows) based mirroring, this is a NIGHTMARE as the mirror rebuilds after the crash. For a long time, no one knew the fix. Now it's easy. You just download the latest windows drivers and management software for the Intel Rapid Storage. In my case, I had to FORCE install the drivers by saying I had a disk, unchecking the compatible only box, and FORCING it to accept the new chipset drivers. That solved my reboot issues. It also let windows see drives over 2TB as their actual size, and use them. The problem was the RAID controller could not use them at their full size...
WARNING: ONLY ATTEMPT THE BELOW IF YOU KNOW WHAT YOU ARE DOING. BACK UP YOUR COMPUTER FIRST! I ALSO RECOMMEND ONLY DOING THE BELOW IF YOUR COMPUTER IS NO LONGER IN WARRANTY BECAUSE THIS WILL VOID IT IF YOU BRICK IT.
From personal experience, as long as you follow the steps, and pick the right files, you will be fine. This is only modding the RAID portion of the bios. So even if you botched it, the system would still POST, it just wouldn't boot.. in which case you can use a dos based utility to reflash your rom.. and I suggest you make a bootable dos based CD with your original rom before you attempt the below.
2) Dell refuses to update even just the raid portion on the bios. They are literally one version behind the version that supports 4TB drives. Well you can fix this in 15-30mins depending on how tech savvy you are.
a) you basically DL your current bios from the dell website
b) follow the instructions here: http://www.win-lite.de/wbb/board208-specials/board281-bios-bios-modding/16658-bios-modding-how-to-update-pci-rom-modules-of-an-ami-phoenix-award-bios/ (all alienware r3 and higher use UEFI bios even if you don't use that function to boot windows)
c) you identify what chipset you have and grab the modded raid bios code and replace the one in your dell bios then use the dell bios uploader to upload it.. and boom... 4TB support along with other goodies (as in full SSD support with TRIM). Since you have the newest Raid Rom, you get all the newer features in the intel rapid storage manger that you didn't see before.
Another thing.. the r3 claims to have full SATA3 support.. It DOES NOT... the controller can not handle 6 Sata 3 devices. It can handle TWO..It does 2 at SATA 3, 2 at SATA 2, and 2 at SATA 1... upgrading the raid and HD controller bios runs all 6 channels at SATA 3 (if you install that mod).