
For many systems administrators, choosing and managing a VPN system is often quite a headache. Inflexible clients, servers, and protocols often prevent VPN's from being smoothly integrated into an already functioning network. The fact that many VPN clients are installed on users' home computers, well out of the reach of the systems administration team, often means that troubleshooting and upgrading VPN systems is time consuming and a struggle for both admins and users.
I have worked with FreesWan Linux and Win2k roadwarriors over NAT and it works like a charm. I guess you need to combine the Freeswan Nat support and IPtables firewall rules
(i prefer using shorewall to get the job done).
Configuring many ports for OPen VPN is a nightmare.