This is at least the second Targus USB 3.0 dock. (There was an ACP-70US - without the "Z" - and before that there was at least one USB 2.0 version of the same basic thing.) I purchased the non-Z version at a local store, and had a lot of trouble with stability of the dock, so I brought it back and bought this newer version.
It is still an unstable product, even with the current (Jan., 2013) firmware and drivers. The audio out dropped more than once a day, so I eventually stopped trying to use it and now plug the speakers into the machine (a Surface Pro) when the dock is being used, ignoring the on-dock audio completely.
And then, about once a day, the dock just "checks out". The hardware is still there, but it's nonresponsive - any peripherals attached aren't really available. The more common case of this is the monitors connected (I'm using both ports) just get frozen with whatever they had, the USB devices slowly drop out (e. g. mouse and keyboard work, but then at some point stop), etc. To fix this you have to unplug the dock from the computer, unplug the power (which at the dock is annoying, because the plug has a sliding, locking connector), plug the power back in, and connect to the computer. Then you're good for another... day if you're lucky.
I am very close to returning this unit and trying a different manufacturer's one at this point. The only thing stopping me right now is the fear that since all of these dual-display docks are basically the same guts (DisplayLink), that I'd be swapping one broken unit for another.
UPDATE IN APRIL, 2013: The very recent April driver update (7.1) has made a substantial difference. I've now gone nearly a week without the sound dropping or the Ethernet dropping. I see other posts about people having the exact same issues I was having, especially the Ethernet. I don't know if the updated drivers would help them, but it helped me. We'll need to see if it's a long term fix but so far at least, it's much better.
Also this is on Windows 8 - I should have said that before. Very specifically it's on a Surface Pro.
UPDATE APRIL 18: The drivers are not perfect still - I have had one drop of the Ethernet earlier this week after all, and just now, a loss of the sound. And there seems to be a new issue with this driver release around performance on the displays - the mouse cursor and scrolling are "jumpy" and that was not the case before. So it's still a work in progress even after all this time. So I am still waiting on DisplayLink to continue their improvements. The device works well enough at this point to not bother sending it back, and DisplayLink powers all of the other devices of this type so it's not like there's a choice around it even if I did send it back. That said I've dropped the rating back because it's a little silly that after all this time there are still issues around it.
I should also mention you CAN'T currently find the updated drivers on the Targus site - I just checked. They are at the DisplayLink site (7.2M0 released April 3, 2013).
UPDATE JUNE 18: The May 2013 drivers are better still. Biggest remaining issue is sound dropping every so often.
UPDATE AUGUST 30: The 7.4M0 drivers (from DisplayLink - Targus still has 7.3M1) seemed better, but audio dropout seemed to get much worse. I ended up completely uninstalling them (after unplugging the dock), rebooting, installing 7.3M1, connecting the dock, waiting for the hardware update and driver load (note: I don't remember seeing the update during an upgrade - that could be a UI issue or an actual installer bug, I don't know), confirming everything was working, disconnecting the dock, uninstalling fully again, rebooting, installing 7.4M0, connecting the dock (again including a hardware update), and then everything was happy for now. We'll see how stable it is. I've dropped my rating because this is a bit ridiculous, not having a reliable driver after all this time.
UPDATE DECEMBER 5: Even at 7.4M2 I'm still seeing the dropouts of audio. I did find a better way to fix it: (1) right-click volume icon in notification area (2) choose "Playback devices" (3) right-click "Speakers - Targus USB Audio" and choose "Properties" (4) change to the Enhancements tab (5) Change any of the enhancement checkboxes, click Apply, then change it back, and click Apply. [The change back isn't necessary but leaves you how you started.] Changing this setting seems to force the driver to sort itself out.