Hot File Clustering with multiple partitions
According to the very detailed OS X internals book and website by Amit Singh, the optimizations for hot files require only HFS+


Ten Things Apple Did To Make Mac OS X Faster 


I seem to recall that only the boot volume was optimized for working sets and hot files, but can't find a good link to any other authoritative document to back up my recollections. We are talking about things written in 2004 and a lot has changed. The good news is that you should be able to find the hfsdebug binary and poke around to your heart's content while analyzing your particular filesystems as you are determining how it is and is not performing. Furthermore, if you partition your boot volume, the hot file "optimization" will be far less helpful than if you just let the entire drive be allocated so that the OS can guess what part of the drive is physically the fastest for access speeds.

Some very astute engineers have opined that 10.6 was the "fastest feeling" OS although I've not seen any good benchmarks comparing 10.6.8 to 10.8.3 or 10.7.5. Snow Leopard clearly doesn't have all the layers of subsystems that Lion and now Mountail Lion have - so from a unix based perspective, you should have great control and understanding of what's going on in the OS most if not all of the time.

I would also be remiss if I didn't mention that you might want to review John Siracusa's awesome reviews of each OS release to read up on the various filesystem performance improvements. Since hot file adaptive clustering was introduced at 10.3, the performance wars have moved on to building smarter storage technologies rather than smarter OS. An especially good article on this aspect would be also from Ars Technica:


How SSDs conquered mobile devices and modern OSes