Why use QLogic's proprietary FC HBA driver and not use the open source version included with your kernel? QLogic's driver has MPIO built-in, so no need to use multipath-tools or another MPIO solution. I only see one SCSI device node in /dev per volume. I also like that the firmware image is include in the kernel module, no need for the hotplug framework to load module firmware (binary blob). There is probably a way to "embed" the firmware image into the open source qla2xxx kernel module too, but I haven't researched it.
I hacked the crap out of this driver to make it work on Gentoo and I'll be honest, I'm quite surprised it even works. So, I definitely would not recommend using this driver for production, although I haven't had any problems running in on my machine (yet).
Compiling/installing QLogic's FC HBA (QLE2462 for me) driver on 2.6.28-gentoo-r5:
Get the package from QLogic's web site (qla2xxx-v8.02.23_4-dist.tgz).
tar xvfz qla2xxx-v8.02.23_4-dist.tgz
patch -p0 < qla2xxx-8.02.23.patch
After the module is installed, a simple 'modprobe qla2xxx' should do the trick. I created an initrd image for my kernel and I can now boot from my SAN.