I have an Ender 3 Pro.
It has the usual slight mods and add ons - glass bed, printed clips, tool holder on top of the PSU, full size SD card reader and metal extruder components. Printing PLA and PETG.
I also have a long-term project to get a Droidworx 1100mm Octocopter frame in the air. As the frame is such good quality I have tried to go the quality route with all components. So - KDE motors, ESCs and 18,5 props, Pixhawk Cube and choice of DJI Ronin (two pilot solution) or HD Air MR Pro - possibly to be controlled by a 3DR Solo “brain” (single pilot semi-autonomous). The rig should carry my Nikon D750 with ease.
I have designed motor mounts for the KDEs. 5215 motors are too big to fit the standard Droidwork mount. I am now at the Mark 10 mount. Escs proved easier. Mark 3 mount seems to work for the 110mm long 75 amp Esc with the cables neatly routed.
The big problem seems to have been either inconsistent extrusion or low quality PETG. That is covered in this thread
I decided to replace the hotend. A £6 metal hot end was on eBay so I ordered one and fitted it. Then I got paid for a couple of jobs done a couple of months ago at Warner Studios - watching kids fight in a pit and being a prisoner in a medieval dungeon. And what is the sensible thing to do with money? Spend it.
So the Ender is being upgraded with:
Direct Drive extruder and metal hot end
Creality v 4.2.7 32 bit motherboard and levelling probe
All this will involve a fairly comprehensive teardown of the machine. So I am taking the opportunity to move the electronics to the back and possibly add a Raspberry Pi for Octoprint. The case is printing while I type this.
The extruder and hot end have to be cooled, So I printed a mount for the probe and ducting for a supplementary 5015 fan from another Thingiverse download. That will become this monstrosity 
Lastly I will be making an enclosure to keep temperatures stable and give me a chance to use a fan to exhaust ABS fumes out of the nearest window. I want to print ABS but at the moment I’m printing in the same room Dogzilla and I relax in - Acrylonitrile Butadiene Styrene probably isn’t the best for either of us to breathe in.
So what am I printing on if the Ender is offline? I acquired a good condition second user Geeetech A30T for the right money and that seems to cope with the problematic PETG very well. The only problem when I first ran it was that with TMC2208 stepper drivers I couldn’t hear the familiar printer sounds (like a 300 baud modem) as it printed. Had to keep checking it hadn’t stopped!
tl;dr
Various problems led to an upgrade and yes, I will be ABS printing soon