Having used an expensive Metcal, I would like someone to develop that level of performance for less. I want the precise thermostat and high quality tips, but I don't solder enough to justify the expense. I am happy to see iFixit driving innovation in this market though. Weller needs some real competition.
How precise are you talking? Usually, cheaper soldering stations get that way by not having a lot of thermal mass, which is particularly needed for desoldering. Otherwise, the PID control tends to keep things good enough. Tuning the PID parameters can make a difference, but once you have a heater and a heat sensor, the software is more or less the same for everyone.