Finally caved in and installed MLPF with ML on my late-2006 Macbook Pro, with 3GB RAM.
While I found the instructions in the beginning of this thread horrible, and for some reason couldn't find the website which I know has existed at some point, I gave it a shot. Turns out that the most reliable instructions are located in the MLPF app itself, and somewhat different from the OP in this thread. The only major problem then, was how obtain the install file for ML. Turns out that the MLPF description is wrong (As I took the naming of the file quite literally) and that the file downloaded from the App Store is called exactly what is required. I used MLPF 0.3 with 10.8.5 from the App Store, and it worked more or less as expected. After installation I didn't get the "Could not finish installation" error as described, but a hard reset and rebooting into the install partion and running MLPF worked as expected (Couldn't restart either again, but again a hard reset did the trick).
ML is now running as expected, and since flash movies in 720p from youtube runs perfectly (Actually, I had problems with full screen flash in Lion, and this is not present anymore!), I expect that hardware acceleration is working. Audio, wireless and bluetooth also appear functioning.
Now I just have to fix Messages, which is the main reason for me trying this out.. 8) Edit: Ran a round of Repair Persmissions, and that fixed it! WOnderfull! 😀
Donated 20$ to the guys behind, and I consider it well spend.
Edit: The machine really seems much faster now with ML over Lion... Could be a fresh install of course, but even with Spotlight indexing, it is very responsive.
Edit: Facetime, iCloud and microphone also working as expected.