As you can see below, I used a blow-off tube with my first batch of beer. The results were fine, but since then, I haven’t used one. I’ve been using a 7 gallon glass carboy as my primary fermenter (which has ample room for expansion so no need to blow-off) and I have a batch going right now where I used a 8 gallon plastic bucket for my primary.

I was persuaded by Kevin at Main Street Homebrew to avoid using a blow-off tube. He has a detailed article here.