Finally some detailed performance data has come available (in MB/s). This data has been produced by Newisys using a RAID 5 configuration and the IOMeter benchmark test:

RAID 5 will have a negative impact on performance vs. RAID 1 or RAID 0. Also the NA-1400 will perform better with more than one concurrent user. The performance for 2-20 users is relatively consistent. There is also no appreciable decline in performance up to the maximum projection of host connections (20).