Looks like SanDisk is selling a 512gb version stateside now and PNY is also offering one of these mini sticks but they only have 256gb.
Ive toyed with this lately using one of the PNY 256 sticks on an MSS and I've come across several challenges that Ricky450 didn't mention.
My first attempts were to simply load the WHS11 OS onto the stick installed in the MSS using an external DVD drive. This worked great right up to the point the OS started looking for the destination drive and wanted a driver for the stick. Worst case I have to start trying drivers and see if something sticks.
Next was a free app called WinToUSB, It apparently works well with w7 but has a usage restriction for server based OS's and requires a $300 purchase.
Second attempt was using AOMEI Partition Assistant Standard. This app is also free will load the WHS11 app onto a stick, but then after plugging it into the MSS, the OS begins but the install hangs when installing devices. To eliminate the issue being stick related (USB3.0 in a USB2.0 port) I tried an install of w7 on a 16gb USB2.0 stick. The install worked but it was uncomfortably slow to navigate the OS.
But there was finally a victory! The MSS will run nt6.1 on the stick.
I'm next installing w7 with USB3.0 drivers slipstreamed in onto the PNY 265gb USB3.0 stick in the hopes that the 2.0 stick wasn't saturating the MSS USB2.0 port and will run faster. If it does, I'll try the slipstream process on WHS11. If not I can either purchase AOMEI Partition Assistant Server (it's on sale at the moment). It will also load an existing install on to the stick.
Or I could try cloning an existing drive and load that onto the stick. Anyhow, it's a fun project...