Windows Server is not required for Storage Spaces, Its available in Windows 8.
I for sure need RAID, because i know how it feels to lose data as i lost my 3 years of works done as freelancer, My Personal information like College Photos, Family Photos etc which you can't get back once lost.
So i use RAID and on top of this i Backup my personal irreplaceable content to Crashplan
And one other feature of Windows 8 most people don't know is Hyper-V, with which you can create Virtual Machines like VMWare Workstation