MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I couldn't get the MK5 drive gear easily in Canada, plus the smaller diameter (6.3 mm in my case) increases the filament drive force and resolution. And, with PLA at least, I get more than enough grip on the filament. 16 kg of pull works out to about 3600 PSI - that's at lot of pressure; I think the hot end will fail before you get that high.
These have turned out to be fairly reliable - neither of my two extruders have failed yet, and I hear Nophead had printed something like 18 + Mendels with his before it gave out. He did have a special hot end though, that put extra load on the mounting tabs, which eventually failed.
Things I'd l
ike to improve would include an easier mounting system (bolt under the stepper is hard to turn), and maybe a higher gear ratio like Adrian's version. Turning it sideways should allow a bigger gear and more Z travel.