I think that glyphs look nice, but they subtley confuse Emacs's UI. In the case
of a two-character glyph condensing into one character's width, the fill-width
indicator -- correctly -- highlights the 81st character as red, but it looks
like it's erroneously highlighting the 80th.
Also when I want to create an anonymous function I type (), which condenses into
the unit character, and it's difficult to delete either the opening or the
closing parenthesis.
Overall I think glyphs are cute, but they're not worth the trouble.