I'm not a mac fan, nor a mac apologist, but I have to say the current Mac Pro beats all of them ... that is an extremely well designed desktop computer. Really a joy to work with.
For runner-up I would say the SGI Octane2, and for a non-desktop machine, the Sun E4500 was an extremely well designed, well manufactured system. Also a real joy to work with (although weighs something like 100 lbs fully loaded)
I hope the Octane2 was better than the Octane. While I like mine, it's really loud, the incandescent bulbs (!) in the light bar don't last very long, there's no room in the large case for a single 5.25" drive, the plastic skins are really fragile, the compression connectors are very delicate, the texture ram likes to unsolder itself, and certain generations of circuit boards fail at a very high rate.
From what little I've seen, Sun gear of a similar vintage seems better built than the Octane.
And a great hardware, with the sliding boards and the pressure connectors. Its only culprit was the missing 5.25'' slot. I still have a dual R12K MXE Octane too :)
For runner-up I would say the SGI Octane2, and for a non-desktop machine, the Sun E4500 was an extremely well designed, well manufactured system. Also a real joy to work with (although weighs something like 100 lbs fully loaded)