I found that the 3.5" squares were way bigger than they needed to be. Unless you feel like you need a lot of extra trimming leeway, 3" should work fine.
Bianca asked about what we like to watch while quilting. I don't have a TV in my sewing space so I don't usually watch anything. My husband and I usually watch something after dinner though, and I hand sew while doing that. Currently we are working our way through Star Trek Next Generation and House. Amongst things that haven't ended, I enjoy The Big Bang Theory, Project Runway, and Game of Thrones.