Today I did an installation of F11 onto a machine with > 300 LUNs visible and available for use. I picked the defaults on the parttype screen and clicked next. After this, I had enough time to talk for a while, go down the hall for a drink, come back, and see that it was still not done. tty4 showed that the storage.log was constantly being written to. I did two tests - one with clicking next to go to the custom partitioning screen, and one with just accepting the defaults. The same behavior was observed each time. Therefore, I believe this is more than just UI slowness but is the underlying autopart algorithm. I have the log files, but they're dozens of megs so I'd rather not attach to a bug.
This bug appears to have been reported against 'rawhide' during the Fedora 13 development cycle. Changing version to '13'. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping
Jeff - this is the bug I was hoping to take a look at on the machine down in the lab with 88 disks visible.