@ntm - Do you still have the unit? I would be VERY curious to know how your RAID 5 test on this page (http://www.ntm1275.f2s.com/synology/synology1010_files/...) would go if you did the mulitple user test with a folder of of small files. I want to create almost exactly this setup but have an office of 5 users who will write files to it simultaneously.
About your power calculations, I think you overestimate the power draw of a "full" computer. I tested around my house using a Kill-a-Watt to measure power draw at the outlet. The workstation I'm writing this on is a dual-processor "core i7" Xeon 5520 system, with Geforce GTX 260, a 15krpm SAS drive as primary OS and six 7200rpm WD Black SATA drives. Its draw at the outlet is 200w idle.
(EDIT: Also 24GB of DDR3 RAM... Plenty of room to reduce the system wattage well below 200w.)
I have an Athlon XP system that has two hard drives and discrete graphics, clocks in at 150w. With a different case, it would be RAID capable.
I'm sure a low-power PC could be built with standard components. It would not get as low as the DS1010+, but the power bill would not be as dramatically high. A laptop with eSATA may actually come close to the DS1010+ power savings while still providing the server flexibility of a full computer.
The power comsumption figures were only supposed to be an example to try to explain that the DS1010+ has excellent figures, but if you substitute your own kw/h figure in to the calculation it will give you a better idea
During my own tests with 5 x Seagate ST31000528AS drives, I get even better figures than Synology's quoted ones
I get 56w in use and 23w in hibernation (Synology figures are 68w in use and 30 in hibernation)