Not denying your experiences, but I've always had the complete opposite experience. I've always marvelled at how smooth PDFs were handled in OS X since days of 10.0 (or so). I can scroll, zoom through simple PDFs like butter (phone bills, etc).
I looked up the most intense PDF I could find. In this case it's a PDF of a front page of my city paper: http://www.smh.com.au/frontpage/2007/04/13/frontpage.pdf.
And, yes, that certainly chugs on my rMBP when zooming in and out (1920 scaled mode).
I grabbed a copy of that and tried it 3 different ways. First was viewing in Safari - very quick and smooth. Second was in Preview - smooth scrolling but a bit jerky with zoom. No beachballs. Third was with Acrobat Reader - very smooth and no lag.
All this on a late 2011 MBP with SSD and lots of memory.