pretty much anything that is terminal based works out of the box.
there are a few things that won't be as happy given the current state
of the term support and there are a few things which make life
interesting on the networking side.  (i'm still waiting for jaguar for
my multicast apps)

the handful of X applications that i actually have an interest in
ported to OS X quite easily.   the XonX stuff is clearly not that
mature but the fact that it's available this early in the product life
cycle is clearly impressive.  

there are going to be rough spots but i've ported several applications
from work which were running quite nicely on solaris/linux/*bsd to
OS X with little problem.  these are pretty standard applications.  if
you're going to port from X -> carbon/cocoa that's a royal pita and
will suck up a ton of time.  however, if you're going to run it on X
on OS X that's a much more straightforward process. the existence of
an X implementation pretty much requires a full fledged Xlib
implementation. 



when last we saw our hero (Sunday, May 26, 2002), 
 Bob Tanner was madly tapping out:
> Quoting steve ulrich (sulrich at botwerks.org):
> > os x provides all of the above.  hell they ship with fetchmail and
> > procmail available by *default*.  the terminal leaves a little to
> > be desired and pretty much anything that you need to build from a
> > unix perspective is available.  
> 
> Available yes, but have you actually tried to compile anything for
> it? The 2 open source projects I work on spend mondo-time trying to
> get an OSX port. Both are pretty xlib intensive. 
> 

-- 
steve ulrich                       sulrich at botwerks.org
PGP: 8D0B 0EE9 E700 A6CF ABA7  AE5F 4FD4 07C9 133B FAFC