eWhisper - 4:19 pm on Jul 15, 2013 (gmt 0)
In most cases, yes.
I've done a lot of talks at Pubcon over the years on this topic, and overall, I'm a big fan of doing both at the same time.
I often see CTR & CR go up when you are twice (or more with universal results) on the page. There is some cannibalization, but in most cases, the 'free' traffic you're now buying is worth the additional traffic you get from paid.
It use to be really easy to do these tests yourself; but its much harder now with (not provided) as you can't see traffic volume on keywords for organic anymore to test the difference between buying and not buying certain words. You can use destination URLs as a bit of a proxy to see the traffic difference to particular URLs with and without the paid traffic, but that proxy isn't 100% accurate.
However, overall, I see a benefit 90%+ of the time.