The only plus is the form and certainly not the function.
Well, the
function is that it includes a MagSafe power supply, webcam, microphone, half-decent speakers, USB, GB Ethernet and Firewire
controllers (not just hubs/port replicators that replace or share bandwidth with your existing ports) and connects that all to your laptop with just 2 plugs. It also enables multi-monitor support for Macbooks that you just can't get with third-party DVI/HDMI/Displayport devices (its about the only non-kludge way you can connect 2 external monitors to a 2011 MacBook).
Apart from one LG Thunderbolt monitor which (I believe) includes a USB controller, the only way to get close to that functionality is to include the cost of a Thunderbolt dock in your calculation, which levels the pricing a bit, and put up with the extra spaghetti.
The display itself is still lovely - as you say, there are screens from the likes of NEC and Eizo that are better suited for pro colour work, but they're at least in the same price bracket (and the sky is the limit) as the ATD and still don't include the extra functionality.
IMHO the only thing that really puts the ATD out of the running now is the lack of USB3 - but that really is a deal-breaker, especially for those of us with pre-USB3 Macs. If, like the thread starter, you need a TB dock to get USB3 anyway, bang goes much of the extra worth of the ATD.