Way too crash-happy, on both Debian and Windows systems. I would love if TeXmacs improves, or has improved, but I absolutely can't recommend it for serious work. I found a particularly nasty case where just changing the type of header (chapter, sub-chapter, etc) crashed TeXmacs and caused all further attempts to open the file to crash the program immediately. And then there was the fact that it was super-easy to crash and lose all your work in an instant.
Finding crap in the toolbars and menu was obtuse, or even what all the keyboard shortcuts were. TeXmacs fails at usability right off the bat, even being unfamiliar to those used to Emacs keyboard chords (it's sort of implied in the name to be for that use-case), and I found it a little better after changing it to a CUA mode (I think it was called 'GNOME Look and Feel'?). Let's grant that the last time I tried to put TeXmacs into serious use was two years ago, but I don't see indicators much of it would have changed.
I really do wish I could agree, but sadly I cannot.