Stable as in 1.8.1, you mean?
Librocket already is included in 1.8.0, which is considered the current stable release (although releases with a zero at the end of the version number are not as stable as the following ones).
Only thing that is not uncluded in the 1,8,0 release is the librocket debugger, which is helpful, but not necessarily required for using rocket.
BTW:
I’m always using snapshots and never had any major problems with anything.