There is another option - NuTCracker from DataFocus. This is
what I get paid to work on in my new day job (that I started last week).
With NuTCRacker, you get a complete porting solution. Many X
applications will compile and run right out of the box, for example.
With a couple of one-line changes, you can build Mosaic. That level
of stuff. It comes with MKS toolkit - the shell is ksh, which is OK for
most things, but if you are used to bash it is a bit lacking.
The fundamental problem with the posix subsystem under NT is
that it is really lame, and MS apparently has no intention of really
fixing it. Their attitude is that all software should be rewritten to
take advantage of NT features anyways, which shouldn't surprise
anyone, I guess. OpenNT is an improvement, but it is still missing
some pieces.
The main thing I would like to see is a shell with job control, but
this is evidently a rather hard problem, as nobody has solved it yet. That
and fvwm for NT (I miss virtual consoles too :-). I met someone once who
claimed that replacing the window manager under NT wasn't out of the question,
but I don't know how much faith to put in what he was saying.
-Eric