Mine came today as well. Quite happy with it. I've got my i5/8/256 installed in it now...
I set the system to display only on the external monitor and it feels just like a desktop. I have it connected to a Dell 30" 3008FWP 2560x1600 display via DisplayPort (standard-to-mini cable), the USB hub in the monitor connected to a full-sized keyboard and the monitor's memory card readers, and to a gigabit ethernet cable.
And I must say, the gigabit ethernet port on it is full-speed -- not like some USB "gigabit" ethernet adapters. I did a 65GB data transfer (Surface system backup) and I saw peaks of near 920Mbit with sustained speeds of 750Mbit.
With the Surface in the dock, the built-in screen off and the keyboard folded up, I'd swear I was using a desktop machine. Color me satisfied.
Add to that, I'm liking very much the Surface Edition Arc mouse. Love how it folds flat to turn off for storing in a case and pairs instantly with the Surface as soon as you turn it on.
I know Microsoft has been having troubles gaining traction with their Surface offerings, but I gotta say the Surface Pro 3 and the accessories they've created for them are pretty much as close to a home run as one can get in the tech business. It's a great piece of hardware and I hope sales are enough to push MS to continue.