I recently put Windows 8 (64bit) on my 15" 2009 MBP. I performed a clean install utilizing Boot Camp. I followed instructions found online. Prior to installing Win8, I had WinXP installed on a partition, which worked perfectly.
For my Win8 installation I upgraded my MBP's OS from Snow Leopard to Mountain Lion. Mountain Lion comes with a newer version of Boot Camp (version 4.0 - I believe). The newer version has a slightly different process for driver installation. It has you create a driver installation disc within the Boot Camp Asstant software running on my Mac BEFORE creating the partition and installation. First it will connect to the interenet and download the latest support files for the drivers for your machine, then it will ask you to insert a blank disc, upon which it will write Windows friendly installation file (the disc contained an executable file [.exe] which is to be run on the newly installed windows parition). While Boot Camp (4.0 or whatever it is that came with Mountain Lion) doesn't have official support for Windows 8, utilizing the Windows 7 installation method will create a Driver CD that works in Win8. After creation of driver disc, follow the normal installation instructions (create partition, install win8). Once Win8 finishes installing, go to the desk top (Windows Button + D), pop in the driver disc and the Executable file. After the file runs the drivers will be installed but will require a reboot in order to be utilized. Reboot your machine and you should be good to go.
NOTE: hold on to that driver disc, I have already had to use it to repair some of my drivers that got messed (my own fault, not mac's or MS) and reran the executable file which fixed everything again.
NOTE: You will be able to utilize much of the drivers in the Win8 environment, however there are limitations. While the trackpad supports multitouch, it is limited (two finger right click, two finger scrolling). The nifty new multitouch gestures in Win8, are not yet supported. I suspect they will be with future updates to these drivers. But we won't get that until Boot Camp can fully support Win8. Also I noticed that my speakers don't switch to headphones when I plug them in, nor does it recognize the toslink connection. I'm still looking for answers to those problems.
For more details regarding the driver support in Windows 8 running on a Mac i found this website useful: