As long as you only keep the Manjaro repos in your system, it is like using it on Arch, which even you Arch the Aur isn't perfect.

Because the Manjaro repos don't sync at the same time with the Arch repos, you might not be able to install/update some Aur packages as the version of X dependency might not match during that time.

But literary, Manjaro has been the most stable distro I've run, even more stable than Arch that recently broke on my system and required manual intervention because of their recent changes on their repo migration.