Apple Issues iMac & MacBook Pro Firmware Updates
Needless to say, a standard hard drive wouldn't be bothered by such a limit, but if you ever decide to replace the stock HDD with a solid state drive, you just might run into a bottleneck. A small cadre of consumers were evidently vocal enough to convince Apple to change things, and now the MacBook Pro EFI Firmware Update 1.7 upcaps the interface to enable the full 3Gbps interface. Apple does mention (rather strongly, even) that any drive that would actually take advantage of the new speed isn't supported by Apple. The entire file is just 3.35MB, so evidently its a simple change of code that uncaps it.
In related news, the iMac EFI Firmware 1.4 Update for 20" and 24" early 2009 iMacs makes those quirks with ATI's Radeon HD 4850 GPU go away. In some cases, machines with that card experienced odd bouts of non-responsiveness, not to mention problems with waking from sleep while in Boot Camp. The 1.7MB download can be found right now and requires OS X version 10.5.6 or later.