It depends if you're run perfmon against a SAN disk subsystem or not?  My experiences have been that the disk queue counters do not provide any meaningful data from a SAN under stress, whereas the i/o completion time is consistant in reporting regardless of SAN or DAS - however SAN's are another subject area. It is possible to have extended i/o completion time without disk queuing so if you only monitor queue you'd never know anything was wrong.

I'm purely considering disk sub system performance and monitoring within a SAN.