Bumblebee doesn't work for me with the experimental NVidia driver. If I use NVidia current, everything is ok.
uname -a Linux adrian-K55VM 3.8.2-030802-generic #201303031906 SMP Mon Mar 4 00:07:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux optirun glxspheres [ 4799.789206] [ERROR]The Bumblebee daemon has not been started yet or the socket path /var/run/bumblebee.socket was incorrect. [ 4799.789252] [ERROR]Could not connect to bumblebee daemon - is it running?
more /var/log/syslog | grep bumblebeed gives this output