I do not have a comparison between the OS X versions but after I switched to a 15" retina MBP and simultaneously to OS X 10.8 the Preview app takes a long time to open pdfs with lots of vectors inside. Also, scrolling is slow, once the file is opened. I did not run into this problem with my old MBP (mid 2007) and 10.7.
Does anyone know a solution or the reason for this problem and whether it is being dealt with?
Here is an example file that causes this problem: https://dl.dropboxusercontent.com/u/119251/methods-rhythmcycle.pdf
edit: Is anyone able to replicate the described phenomenon with the above supplied file?
edit2: Can someone please try to open the file with a rMBP (preferably 15")?