Known issues with using Ltk:

Windows

It seems to be impossilbe to use Ltk while internet via AOL is active.
Similiarly, some programs that hook into the system (like tray utilities) 
seem to hinder Ltk. (Ltk needs pipes to communicate with the Tk process, 
so programs fiddling with low level operations may influence that)

 List of programs, which can prevent Ltk from running:
 
 o babylon
 o The Wonderful Icon


Mac OS X

In general TkAqua runs very nicely and behaves very well as a
native program should, using Aqua widgets and even putting the
menues in the Mac menu bar. Only caveat with TkAqua is, that
the screen updates only in intervals, so programs which require
very fast interactions with the user seem laggy (cpu usage is
still very low, so I assume it has something to do with the
update frequency). A way to mostly remedy the problem is 
to use the X11 Tk (which looks as old-fashioned as every 
Unix Tk does, but has faster response times. It can be
installed via Fink. To use it, the lisp program only needs
to set *wish-pathname* to /sw/bin/wish. You might need
to put export DISPLAY=:0.0 into your .bashrc.