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.)
http://sourceforge.net/tracker/?func=detail&aid=2816874&group_id=235725&atid=1097639
And http://blog.esync.org/2009/09/tuntap-kext-for-snow-leopard-x32x64.html
Finally, the official project page:
http://tuntaposx.sourceforge.net/
