Here comes a Hurd of skeletons out of my closet! Being a very marginal Hurd hacker myself, I couldn't let some of the remarks about the Hurd pass. Most of the things below have been better written of elsewhere by more competent people (the Hurd Wiki for example) but here goes anyway...
although proof of this world-shattering marvel seems to be long in coming. Hurd's Mach kernel's been out, what, a year and more?
The Mach micro-kernel is what the Hurd runs on the top of. In some ways Hurd/Mach is more like Apache/Linux. Mach is not a part of the Hurd. The newer Hurd runs over the top of a version of Mach built using Utah's "oskit". Others have run the "Hurd" over "L-4" and other micro-kernels.
The lack of hardware and other support in the existing micro-kernels is certainly one of things that is holding back the common acceptance of the Hurd. (For example neither "mach" nor "oskit" have support for my video card--i810--for which support came late in the Linux 2.2 series).
Now, if only Linux was written in a sufficiently "de-coupled" way to allow the stripping away of the file-system and execution system, we would have a good micro-kernel already! The way things are, the "oskit" guys are perenially playing catch-up to incorporate Linux kernel drivers. Since these drivers are not sufficiently de-coupled they are harder to incorporate.
One the other side Linux "interferes too much" with user processes making Hurd/Linux quite hard and probably impossible---but one can dream...
That's the key, AFAIC; a 99% solution that's being worked on by thousands of people is miles better than a 100% solution that's still under development. It's one of the things I love most about Linux; the amazing roiling, boiling cauldron of creative ideas I see implemented in each new kernel and presented on Freshmeat.<grin>
The damn thing's alive, I tell ya.
What you are saying is true and is (according to me) the reason why people will be running the Hurd a few years from now!
The point is that many features of micro-kernels (such as a user-process running it's own filesystem and execution system a la user-mode-linux) are becoming features of Linux. At some point folks will say "Wait a minute! I'm only using the (micro) kernel part of Linux as root. Why don't I move all the other stuff into user space?" At this point they will be running the Hurd/Linux or something like it.
Think of the situation in 89-91 when folks on DOS or Minix were jumping through hoops in order to make their boxes run gcc and emacs. Suddenly, the hoops could be removed because of Linux. The same way the "coupled" parts of Linux are preventing some people from doing things they would like to do with their system. As more people are obstructed by those parts---voila Linux becomes (or gives way to) a micro-kernel based system.
Didn't someone say "... and the state shall wither away".
When speculation has done its worst, two plus two still equals four. -- S. Johnson
... and I still run GNU/Linux! -- me