The drives can be swapped without any tools. My only regret was the 2GB ram limit due to the outdated chipset -- it scares me a little that i'm running ZFS with less than the 6GB recommended minimum FreeNAS recommends, but I'd rather use ZFS than worry about RAID bitrot/etc.
With the Evercube, I pay double for 2.5" storage and have no redundancy? 5TB of storage but only 512MB for the OS? At those prices the OS storage should be at least 1GB so that users have more options. Standard Ubuntu Minimal requires a lot of manual configuration (no room for GUI in 512MB), especially if you want network sharing and RAID. Then, because it's Ubuntu I can guarantee that there will be major changes in the configuration process at the next version upgrade.
Compare this with ZFS on BSD/Solaris which exports NFS shares with a single command. Upgrade process is predictable and requires little intervention.
Or compare with my setup: Arch Linux with ZFS-FUSE in RAIDZ2 configuration: 4x2TB HDD = 7TB of storage that can survive dual drive failure. And just the Evercube shell without drives costs much more than my setup!
Whoever buys the Evercube will be looking for a pretty solution instead of a technically solid one. Ubuntu 9.04 is outdated and no longer supported. To spend this money and go this far on design on hardware, and then fall so flat on software is really disappointing.
Uhh, 4 x 2TB raidz2 will give you 3.6TB of storage...
About the only issue with NAS devices is disk encryption, but at that point, you probably require a NetApp box or similar.