After writing my reply and decided to go back and search my records to see if I had actually setup a ROUTE in 10.8 and I did. I wanted my VPN to not be the primary route so I created " /etc/ppp/ip-up " file. What it does is add the route when the VPN comes up and gets deleted when you disconnect from the VPN.
ip-up file contains this. The 10.1.1.0 would be your office network (IE - network you are connection to via the VPN). You could have multiple if you have multiple networks at the office. Again, this allows for you to only have tcpip traffic for 10.1.1.0 to go through the VPN. Just set the service order of your vpn after you network connection. Also, do not set the advanced setting which says to send all tcpip traffic over the vpn.
#!/bin/sh
/sbin/route add -net 10.1.1 -interface ppp0