I rode with panniers for a few years, couldn't see riding with a backpack. Moved to a much more temperate climate and I ended up with an ortlieb backpack to commute in with. It's not bad but not great. I do get warm, and I notice it on my shoulders after about 15 miles. The panniers are superior for me on longer rides, but I also get to pick any bike I want in the morning when I'm using the backpack, and if I stop somewhere I don't need to take anything off the bike.