If you do a regtest-comparison between builds with guile-1 and
guile-2, nothing serious is visible in the images. So far one could
say "well enough".
Though, looking through the other results, some other flaws are noticeble.
One I remember immediately is the not working 'procedure-source'. It's
simply disabled in guile-2, see
https://lists.gnu.org/archive/html/guile-user/2012-09/msg00020.html
So with guile-2:
\void
\displayLilyMusic
\applyContext #(lambda (ctx) (ly:context-set-property ctx 'fontSize 6))
-> \applyContext ##f
I think there were more, but I would need to redo the regtest to be sure.