I wrote a patch to add AEAD cipher modes to OpenVPN. This is one of NIST's recommended modes and newer Intel chips supporting the AES-NI (with PCLMULQDQ) have excellent support for acceleration in this mode. I posted the initial version at https://community.openvpn.net/openvpn/ticket/301 and that ticket has some of the performance numbers on an Ivy Bridge class chip.
It also doesn't appear PolarSSL has added AES-GCM to their main crypto API yet. (You can also comment at Github at https://github.com/kruton/openvpn/commit/a8c6701c8b47429c32da5c01f4398f9e0b293c01)
