For me, the hardest part was getting my cannon multifunctional printer recognized. It wasn't too hard, but it is an older printer that is hooked up through a wireless print server. I had to figure out that wireless usb1 that was present needed to be associated with the canon pixma mp780 printer driver built into snow leopard. Oddly, the installation automatically recognized and took care of this for me for my HP laser printer (which is wireless usb 2 on the print server). Overall, a pretty painless install.

That being said, I am not noticing a huge difference in speed for most of my applications. I think aperture is noticeably faster for dealing with raw images.