So I got mine all together today. I'm sure it's pretty quiet for a server type chassis. However, it's not quiet. I would not want to use it as a desktop. The 120mm fans have a definite pitchy whine to them even when they're spun way down. They definitely don't have a reasonably pleasant broadband whoosh sound that good fans make.
I'm pretty sure my neighbors will know when I fire it up when the fans go full throttle for a few seconds before spinning down.
I don't know how loud it is under load. I haven't gotten that far. Right now I'm doing "bare metal" testing with it to make sure the RAM is all good and working before I install an OS.
However, the Intel chassis, ducting, passive heatsinks, and all that stuff went together very nicely. You can tell Intel did a nice job engineering it all.
Thanks again for pointing out the OEM XS stuff on eBay to complete the system!