I own and use the TMT-2000s daily. Here's a bit of info' and my experience of it: Firstly, the time from out of the stand to melting solder on a 2.4mm chisel tip is 10 seconds. Its worth noting that when the iron is placed back into the stand it turns off, there is no reduced temperature period like some other irons such as the KSGER types etc, so its 10 seconds to re-heat if you leave it in the stand to the point where it gets cold. In real usage assembling parts on a PCB this time is less as the tip seldom gets cold in the stand.
As for heat transfer - it is a powerhouse. Even a relatively fine tip will dump plenty of heat quickly into a joint, which leads me to another point. Don't go crazy buying lots of tips with different thermal masses like you would with a regular iron. I use only 4 tips for 99% of my work, a 1.5mm bent chisel, a 2.4mm chisel, 1.2mm chisel and a long reach 0.5mm conical. I have the 5mm chisel but its overkill unless you are soldering onto a metal chassis, TO-220+ tabs to a heavy thermal mass, or de-soldering large heat sinks from PCB's. Tip durability is excellent, and I like the handle ergonomics. The stand is thermoplastic but is solid and durable, I have no issues with it. The microswitch in the stand is accessible so could be replaced in the event of a failure. RF emissions from the unit are so low as to be negligible. The power unit is built like a brick, it might look dated but it is smaller than you might expect and unobtrusive.
If you purchase one pay attention to tip temperature rating options when buying tips (60 Series 325°C - 358°C, 70 Series 350°C - 398°C, 80 Series 420°C - 475°C), tip life will likely be longer for the lower temp' tips. Tips are also cross-compatible with Metcal ones so shop around. Overall I'm very happy with it and not having to bother with settings is great. I have only 2 minor niggles, due to the switch in the stand there is a cable from the stand to the power unit, this restricts stand placement to the reach of the cable. The recess in the stand for brass wool is smaller than I would like. I'm not concerned about obsolescence, there are lots of even older units still in industry scale use. Personally I think Metcal's move to temp' control in their new units is a step backwards.