I got the Metcal MX500 setup and working and am very impressed. This is the first time I see a Metcal in person, most of the solder irons I used so far were Wellers. My configuration include a used MX500P from ebay (a European model with the internal jumpers changed to 110VAC), this base and handpiece from amazon
http://amzn.com/B001BY4848 (does not come with a tip) , a STTC-122 tip and a STTC-125 tip on order.
The power supply is built like a Russian tank, made of cast metal and built to last. The components inside are easily available through-hole (no fancy microcontroller, etc), the circuit is straight forward (schematic and description are available online) and I even managed to take it apart and fix the green LED that did not work. Operation is very simple, an on/off switch, an A/B switch for the two power outputs, a hidden setup screw to disable the auto shutoff (not using it), and temperature control by replacing the tips (which means that calibration is never required).
The handpiece is super light, cable is smooth and flexible (looks like a rubber tube), the tip is short and close to the handle which makes it easy to control. Tips are easy to replace (just pull out), the base is wide and well constructed, it include place holders for few tips and a magnet that reduce the tip temperature while 'parked'. The range of available tips is amazing and many are available on ebay for a more reasonable price (the tips are expensive compared to other units I have used).
Soldering with it is really enjoyable, it transfers the heat and melts the solder like butter. I expected a good product but it exceeded my expectations.
Cons:
- Unit and tip price (got used on ebay to mitigate)
- Slight hamming (I tightened the internal 4 screws that hold the transformer and it is much better now).
- Big an heavy (I actually like it this way, it sit stable on the desk, and has a hidden handle to carry it around)
- No temperature setting (I had it on my last Weller and did not know how to set it up so left it on 700F).
- The main switch is on the transformer's secondary, so some power consumption even when powered off (yak)