I had a lot of misrable time with WinEmacs some time ago.  The point is
that there is nothing much that WinEmacs cannot do and GNU Emacs can - but
many Lisp users are research people that almost always work in a Unix
environment as well - and have their own (possibly large & complex) GNU
Emacs configurations.  This is the situation I had to live with - having
my 'oficcial' files on Unix, and some quick hack for the WinEmacs with many
bugs that I didn't have time to work on.
Another point is the process communication using files that tends to be
highly unreliable - this is probably not something that will be better with
GNU, but the DDE interface should be better - and it works only on the new
WinEmacs version - and you don't get that from Allegro if you buy the site-
license version.
This makes the last point - GNU Emacs is free, so you get updates, bug fixes
etc. with convenience - that is the main disadvantage of using WinEmacs.

                                                                  Eli Barzilay:
                                                                  Maze is Life!