Review

First generally speaking I am amazed and stunned by complete system. So yes I am subjective.
But for me it is that good.

Now I can speak only about C245906, C245770 and C245931..... for now. As it seems there gores another black hole that I can sink tons of money in :).

906 - general more accurate soldering tip. To naked eye from a little distance it looks like a conical tip but it still keeps it's native chisel form. Under the magnification you can see and use it's native strength. It i very small but can heat up big things. Very fast ramp up speed.

770 - Jack of all (many) trades. It is wide enough to be used as general purpose soldering iron and even solder bigger things with it. On other side it is flat enough to do some things in SMD scenario. You can use wick and clean pads with it and you can even solder few pins a time by dragging it over the pins. You can solder anchor points of the connectors with it or heat up to220 and solder it to the ground plane. It is thin profile chisel. In a pinch this flatness can be useful if you do not have a knife soldering tip and you really need it (do not damage it though, it is not meant to cut or scrape things mechanically with it). It handles Potmeter housing so easy. It solders cables easy. It solders TH components easy to.
Turns to be more and more my favorite soldering tip now days. Before I was all about accurate cone tip but now I am turning to 770 more then to any other tip.
Ramp up speed is good and it contains enough thermal reserve / has good active heater that it can do nice things.

931. It is best when you use it for what it was designed. Drag soldering of QFP pins. In the retrospect 965 would have been the better choice. This one is to big in some scenarios where nearby components do not allow you to use 931. I guess you can use it for other things as well but then again why if you have the other tips.
Ramp up speed is good.

After this 3 points I just understood that I want few more variants :( Thanks JBC :) here is my money take it :)