I have been looking forward to this one for a long time; so far, very impressed! I got it with the new Obsidian Light (my notes on the new vs old O.L.:
http://www.saberforum.com/index.php?topic=48816.0).
It is long at 14 inches, but it is light enough to easily use in one hand. The upper grip is very comfortable and well balanced (using a Ultra Edge 36 heavy grade blade). The extra length and lower grip make 2 handed very light and comfortable. I split my grip (right hand top grip, left on bottom) so my hands are separated like using a Japanese sword.
In addition to the grips being very comfortable, I got an AV switch so there are no raised or "hot spots" on the blade. This is a major selling point for me; there are plenty of amazing looking hilts from an artistic perspective, but I like to be able to pass it hand to hand etc. without too much concern re: hand placement.
One downer (because nothing can be too perfect) – the newer Dark Arbiter do NOT unscrew in the middle (it is now 3 pieces, not 4). It has the MHS pommel and emitter, but you can no longer remove the upper grip. I was a bit disappointed as I am an MHS nut (making wacky combinations) and because I wanted to see how it felt in one hand with the emitter connected directly to the body. :: sad nerd noises :: I spoke with tech support and they are going to update the webpage/reviews to reflect the change for future buyers.
Over all, this is my favorite US so far. Highly recommended!