Hi uroni,
Wow, that was fast 
Yes your new client uninstaller works great. Thank you!
Btw. The installer script add system startup for /etc/init.d/urbackupclientbackend …
/etc/rc0.d/K20urbackupclientbackend -> …/init.d/urbackupclientbackend
[/etc/rc0.d - /etc/rc6.d]
These files are still present, maybe you want to add them to the new /usr/local/sbin/uninstall_urbackupclient.
Bob