eljay,
Just because you do not support 802.11b clients does not mean they are not in the area, somewhere. Airwave only sees clients that actually associate, not clients that merely scan. If someone brings in an 802.11b client but it does not associate, it is still seen by clients and access points, NOT airwave necessarily. If you don't believe that you have any 802.11b devices, but there is the small possibility that someone is carrying one, why not let a time-honored mechanism used to protect those clients and your performance continue to perform? We have observed so many users disable mechanisms that are necessary for their network to run and when it is time to troubleshoot, they are not able to actually tell us why they are disabled... This is not a feature.. It is part of the 802.11 spec...
Again, the ability to disable this is only because other manufacturers have it, NOT because it would improve performance.