The longer boot time in Mountain Lion is caused by AppleAHCIPort.kext and IOAHCIFamily.kext, two kexts that Mac OS X uses to read and write to your computer's hard disks. If you replace these two Mountain Lion kexts with the kexts that were used back in Lion, the boot time goes back to normal. Here's how to do just that:
LATEST UPDATE (August 25, 2012): This fix only works for OS X Mountain Lion 10.8.0; the it does not work in newer versions. If you do apply this fix in 10.8.0, you will have to un-apply it before updating OS X. Otherwise, Mountain Lion will not be able to boot. You can do this by reinstalling the original versions of the two mentioned kexts.
First, you need the versions of these kexts that were used in Mac OS X Lion. You can download these kexts below.
DOWNLOAD: Lion kexts
Open Kextbeast, click through the confirmation screens, and install the two downloaded kexts.
NOTE: If your Hackintosh uses an SSD, you will have to reinstall TRIM Enabler in Multibeast after performing this fix.