98% of the crosscutting I do (depending on the size with my CMS, crosscut TS
sled, or with a guide and a circular saw) is 90 degrees in both directions.

I understand that RAS can be fussy to set up, but if set up properly will
they do decent 90 degree cuts? Or are they just inherently inaccurate? I
don't mind spending an extra 10 minutes on the rare occasion I want to do
something more exotic; especially since it would take much longer to do it
now (at least on stuff bigger than my CMS).

I have my eye on a 2 year old craftsman that was barely used. Sure would be
nice to be able to do 16" crosscuts without a lot of fuss; but if it won't
be accurate, then it would just be a waste of room and money.