The TB16 Thunderbolt dock that I have used successful with a XPS 15 9550 is currently also functional with a new Alienware 13 R3. However there are a few issues. I'll list the different (from XPS15) behavior I observe here and hope others would chime in on this particular combination:
(1) The thunderbolt cable's light doesn't come on and the Alienware doesn't charge. I know the power limitations of the dock but was hoping it would at least trickle change.
(2) USB ports on the dock, and those on the external display (connected to a USB port on the dock) work but with artifacts. The keyboard is exhibiting a "sudden key repeat" problem, where it would all of a sudden spew out the same key (as if the key Up event were lost somehow). It's more of a problem is the "sudden repeat" is with Backspace.
(3) Again with USB, plugging in a device can knock other devices out, such as, I plug in a webcam, and the mouse (a Razer Orochi on wired connection) would stop working.
(4) The external display (via HDMI on the dock) works. This is the smoothest part: it just worked from get go.