Alas for one, this is the first product I know of Hakko's where the improvement is more a Rube Goldberg for the 888's target market [ I'd forgive the stickers its gave away for the 936 before it was discontinued] rather than technology with truly improved solder functionality.
One could say, this 888D is a recycling the old Hakko 937 controller system. Which was much more expensive and except for digital locks placed on adjusting set temp, offered no more functionality than the analog version, 936.
If a power-on light was really all that was needed, it simpler to add it than redesign the controller for a digital readout. Without redesign you can change the off/on switch to a lighted one easily too, a literal drop in replacement without any fuss.
What preset "temps" do users actually get? The pencil heater-feedback design used in the 936/FX888 isn't
really accurate to the 1C resolution the LED display for
tip temperature because the temp sensor is at the bottom of the tip assembly, and is subject to some temperature offset. Further this tip temp changes with use and wear, so this design requires periodic manual re-calibration. So the LSD will be off after just a few uses, but that usually isn't bad enough to require recalibration, but it won't be accurate. That's why on the the 936, the original marks were at
50 degree positions, and the FX888 was already overkill at 10 deg marks.
The digital readout is just a fancy representation of what could have just been painted on the faceplate. If one wanted presets on an FX888 just mark the scale with Sharpie pen or masking tape to where on the scale you want the temp for a task and you can even label it with more text.
Why all the groaning?
As best I can tell, the iron finally has an ON/OFF indicator
I like the presets because on the occasion that I turn it up (to handle a heavy joint) I'm never sure that I quite remember the original setting. Anyway, I suspect that I shouldn't be changing temps to do that anyway, I should be changing tip mass. The temp should be set according to solder spec, no?