Because performance is a regularly mentioned subject, here some appromximate figures from my environment (SATA HDD greeen @ 5400 rpm [except USB HDD @ 7200 rpm], Giga-bit LAN, JBod 2x HDD). The desktop used for below test is 8 years old (Intel P4 @ 2.4GHz etc).
This is not a scientific measure (drag & drop, clock) and also heavily depends on the respective environment. Personally, for the moment I am not so much worried about this performance because I use this NAS more as location of reference (with =< 2 concurrent users) than interactive work folder.
My results PC with i7 3770k, 2x ADATA P900 in Raid 0; 2x 1GB hitachi HDDs inside the NAS. Tested with 10/100 switch, Gigabit Switch, and Pc directly connected to NAS. Tested performances of RAID 0, RAID 1 and JBOD.
Ahh almost forgot, test subject was a 2 GB single file and used Samba method