Hello all,
I use it on a bunch of Printr Metals for teaching middle school students about 3D printing. I love BuildTak, protects the extruder and bed, good adhesion, and a little glue stick goes a long way for tough prints. Mostly printing PLA and a little ABS, unheated beds.
I print a ton on NinjaFlex on heated glass, and it is pretty sticky, no adhesion problems. Haven't tried on a simple, wrong kind of extruder head.

What I am curious about is the new Igus iglidur-170, as it may be hard to get to stick. Just got a small sample to try. This may be a popular filament with FRC robotics teams, they all got a small sample and if it is as tough and slippery as billed, I think it will be popular for a wide variety of custom slides and bearings.

I'l have a better idea after I print, starting with the M2, then Simple and finally a Cubify Eko that teams got last year.

Bob