Hi Jimp:
I have two FW-7551 devices set up, with an Ethernet cable directly connecting the WAN ports. They came pre-loaded with PFSense 2.2 and AES-NI is enabled in the BIOS on both devices. AES hardware support is also enabled in the System>Advanced>Miscellaneous section.
I successfully built an OpenVPN tunnel through the devices using AES-128-CBC, SHA1 and the BSD Cryptodev engine. Oddly, the maximum transfer rate I can achieve with an encrypted tunnel is 100 Mb/s. The AES-NI support makes no difference in throughput. If I turn encryption off, the rate increases to 200 Mb/s.
I changed many parameters in the Open VPN setup and turned AES-NI support in PFSense on and off, but the peak transfer rate stayed at 100 Mb/s. I do not have any explicit traffic shaping defined.
I used two Windows laptops (one at each end of the tunnel) to exercise the link. When the computers were connected directly to the Ethernet switch, I saw transfer rates approaching wire speed (800-850 Mb/s). When connected via the tunnel, the rate was the previously mentioned 100 Mb/s.
At this point I'm a little mystified, since I would have expected the transfer rate to be a little higher, especially with encryption turned off.
Cheers,
Ed