I've been spending some time to get Mountain Lion to run on my late 2008 white Macbook. (MacBook 4,1). I tried MacPostFactor, but that fails to produce a USB stick or -drive which boots my old little 'Book. So I decided to try the old MLPostFactor (v0.3). And I'm happy to report that it has been succesful: it now boots Mountain Lion, and everything (except SMB connections to Windows shares, the known issue) works. And performs quite well, as it's equipped with an SSD and 4GB RAM.
I'd be interested in solving the SMB issues but other than that, I'm very pleased. I did have to call Apple support to have them enable Facetime on the MacBook, but other than that, it works surprisingly well. I've spent some time replacing a lot of icons and graphics by those of Yosemite (so that it looks more or less identical to my iMac, which is running 10.10).
The main reason for doing this officially unsupported upgrade is the ability to run iMessage and the improved iCloud support.