My DH61AG came this afternoon. I've been waiting for something like this ever since SPCR's Intel D945GSEJT review a couple of years ago. The goal of having an extremely low power desktop that is also very fast (I run a lot of compilers/development tools) is an obsession for me. I'm not going to get around to messing with it much until this weekend, but here are my observations so far.
System Configuration
------------------------
Intel DH61AG Thin Mini-ITX LGA 1155 Motherboard
Intel G620 Pentium CPU + Stock HSF
2 x DDR3 1066 SODIMM (1.5V)
Samsung 470 SSD (64GB)
Dell PA-3E 90W Laptop Power Adapter
1) Running with Ubuntu 10.04 I see 18W at idle (measured via Kill-A-Watt at wall)
2) The CPU socket is not where it is on a "normal" Mini-ITX motherboard. It was supposed to go in a Raidmax ITX-0907-BP case I have, but the HSF runs into a support bar in the case:
http://www.frys.com/product/61458693) With default settings the stock HSF is not silent. It is quiet, just not silent.
4) One nice touch which I wasn't expecting in the box was a SATA power cable which you need because you power your drives directly off the motherboard.
5) The technical docs on Intel's site are good. If you're interested in this board, look through the docs in detail because the board has many non-standard features relative to an ITX MB that is just a sawed off version of a MicroATX MB:
http://www.intel.com/products/desktop/m ... 8dh61ag%296) I have a Dell Inspiron 17R (the current second generation Sandy Bridge model) and I'm using the 17R's power supply to power the DH61AG. So I can confirm that the Dell power supplies have the right barrel connector to mate with the DH61AG. The spec for the Dell (barrel) is 7.4mm outer diameter, 5mm inner diameter. That was my biggest worry when making this purchase, so I'm really happy that it worked out.
7) This combination of components (with the Samsung 470 SSD) flies, after the BIOS boot screen you get to the Ubuntu desktop in about 2 seconds (if that).

My Dell 17R (Core i5 2410M, 4GB DDR3 1333 w/2 DIMMs, 500GB 5400RPM notebook drive) idles at 8-9W with the screen off while driving a 1920 x 1200 monitor via HDMI. It is a good comparison because it is of the same second generation Sandy Bridge architecture and I'm using the same DC power supply. So while the DH61AG is a more laptop-like design (single DC power in, DC-DC conversion directly on motherboard) than a normal desktop PC, actual power use is between a normal desktop and a laptop. BTW, after I got my 17R for home I got a couple Vostro 3750s at work. They are essentially the same laptop in different cases. The 3750 also has a fingerprint sensor, gigabit ENET (instead of 10/100 on the 17R) and an ExpressCard slot. But the biggest difference for me is that 3750 has a screwed in panel so you can get to the hard drive easily while on the 17R you have to basically have to disassembly your entire laptop to swap hard drives. It's crazy, you can see the hard drive on the 17R through its ventillation holes but you can't get to it.