I ran 2x4GB Samsung 2RX8 PC3-10600S DDR3 SODIM (1333 MHz) ram on my mid 2009 MBP for 2 years. I bought it and had it installed at a small computer shop before I'd ever looked into anything about ram.
The computer ran very well (night and day compared to the 2GB I bought it with). I used office applications in both OSX and Windows (bootcamp), but mainly ran in Windows for my work. Nothing graphics intensive, except maybe google earth...
In late 2011, I downloaded a google earth upgrade. The new google earth looked more fancy, but would crash after about 20 seconds every time I opened it. I stopped using google earth.
I recently cleared my drive (incidental), installed Snow Leopard from scratch, and found that google earth was still unusable. I recently swapped the Samsung ram with two 4GB 1066 Kingston chips, "Specific Memory for Apple (KTA-MB1066K2/8G)". I'd researched and purchased the chips (after my upgrade) for my wife's Macbook, and she now has a new computer. Google earth now works great.
Now that I know, I wouldn never buy overclocked ram again. However if I had 8GB of 1333 lying around and only 2GB of 1066 in my 2009 MBP, I would certainly run the overclocked 8GB and deal with the occasional bugs.