VPN passthrough is provided for PPTP and IPsec and now also L2TP. All are enabled by default and separate disables are provided on the Security > VPN page. Linksys says multiple passthrough sessions are supported for each VPN type and tunnels can terminate at multiple remote gateways.
Port forwarding is supported for one IPsec and L2TP server if you want to host your own VPN gateways. But if you're looking to host a PPTP server, you can't, since port forwarding isn't supported for the special protocol that PPTP requires.
Logging & Other Features
The GS' logging features are the usual Inbound and Outbound traffic logs that you've come to expect with Linksys routers. Note, though, that neither Linksys' SNMP Trap mechanism nor syslog daemons are supported for external log analysis and storage. You also can't save logs to a file, but you can clear them.
Other features include the ability to disable the Internet Sharing function and use the GS as a non-NAT router. When in this mode, you also get to control the interfaces (but not the direction) that Dynamic Routing RIP-1 and 2 messages are allowed on. You can also define up to 20 Static Routes in either Gateway or Router modes.
That wraps up the firewall's features. Let's move on to routing performance.