Snow Leopard Notes - tuntap
The only thing I'm really worried about related to upgrading to Snow Leopard is the tun/tap driver which is used by OpenVPN.
But I learned two things today.
First, tuntap is available in macports.
sudo port install tuntaposx
Second, some folks have already patched it for Snow Leopard. (It seems my fears were founded, and it did not work.)
Finally, the official project page: