I actuallly have two machines. Both have extruders which I've printed myself, and both were improved a lot. The Orca was my first printer, but nearly nothing except the basic frame and the Z-Axis is from the basic kit anymore. New extruder, new linear bearings, different electronics, new stepper controll, new heated bed, new toothed belts and new software. I cannot really recommend the Orca to anyone, there are some mechanical flaws in the design which make really good prints difficult. I tend to print fast with it, with a 0.6 mm nozzle. At least it's no longer as loud as in the first videos. 

My second machine in an Ordbot Hadron, which is made from Makerslides. Much better design, this is the one I use for best quality. The nozzle is 0.4 mm, so the prints are finer by default. This is the machine I use most of the time, the Orca will most probably rebuild as soon as I find the time.

But I've seen many different designs - we have an user group here, and the people here use very different printers. One Ultimaker, a Makerbot, a China Makerbot Clone, some Prusa Mendels, a T-Rex (Mendel 90 from aluminium extrusions), some other designs as well. So I do have a little experience about what works and what doesn't. 

And I hear ya about ball screws. Kind of expensive stuff, but I think the quality of the Z axis will be much better with it. They are on my list for the next printer's Z axis.

 

 

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.