TeXmacs is a really interesting and fun product. Tried several times. Love its idea. There are lots of bugs last time I tried. Glad to see it is moving forward.
I'm not sure when you tried, but I'm using it since 2006 and although there are bugs we are steadily improving it and personally I (and many others) use it everyday and do not experience any serious issue, especially in the last versions. Please realize that TeXmacs is a complex piece of software (is typesetting engine + macro language + UI interface together) so is more difficult to maintain than each piece separately.
And I've fixed some of them by myself or with the help of other contributors.
Please report bugs to https://savannah.gnu.org/bugs/?group=texmacs
And we will fix it as soon as possible.
For the next release: TeXmacs 2.1, we mainly focus on bug fixes.