Some final updates before I leave this thread alone...
The thread linked to by Rico has been undergoing lots of activity and is very useful (readers of this thread should check it out).
I have had further problems with the qlogic driver, but they are now gone. Basically, once you configure the MTU manually on the interface, the issue goes away.
The first time you do it, you have to wait for multi-user mode to happen, then open up the second virtual console (Ctrl+alt+f2), login, and go to a shell (option 8). In the shell, bring the interface down:
ifconfig ql0 down
Then set the MTU. You can set it to 1500 or 9000, depending on your preferences. Most likely you'll want it at 9000 eventually.
ifconfig ql0 mtu 9000
ifconfig ql0 up
This should get rid of the console going crazy and allow the interface to work. Then you can get into the web interface and configure the MTU for that interface via the web gui. Don't forget to do this step.
Unfortunately, I can't get anywhere near 10gbps performance on this card. The best I've been able to do after lots of tuning (sysctl, tunables, loader.conf.local) is 4gbps, which only worked for a bit and then it went back. It's difficult to figure out why; it's not a card issue probably. It's most likely the hardware and the config (as well as the other end of the connection). I've got it connected to a 10G module in a Brocade FLS624.
There is a known freeBSD bug that causes the MTU issue - I expect it will get patched in pfsense before long. For now, the above fix should work.