tl;dr: I like the mosquito hotend
I purchased the Mosquito hotend because I often had issues with heat creep during prints with PLA. In the last 200h I had not a single issue with heat creep.
I was a bit concerned about the mechanical properties of my extruder body (PETG) during prints at temperatures around 240°C with closed printer housing. The temperature of the heatsink can rise up close to the glass transition temperature of the PETG.
By now, nothing happened. The hotend still sits firmly inside the extruder body.
I could not see any difference in printing quality compared to the stock hotend (E3D v6).
tbd: It should be possible to print models with a very fine resolution in Z-axis without the risk of heat creep (increasing the resolution = decreasing the volumetric flow rate)
When I tried to play around with wood filled PLA, once it resulted in a clogged nozzle. Because I did not recognized it directly, the filament was grinded by the hobbed gears, so I could not remove the filament by the unload function of the printer.
To remove the remaining filament I just removed the nozzle (with one hand) used new filament to push the remaining filament through the hotend and screwed in a new nozzle (with one hand).
Compared to the stock hotend, it is very easy... almost fun.
I have considered to buy the Mosquito hotend for a long time. Finally I bought it and I do not regret it. I had to pay a lot of money for the hotend, but it is worth every € I spend.
I am also happy, that I could improve my designing skills during this project.