I do the same speeds as you, Linsey. Sometimes if I don't feel like running at all I up the walk to 4 mph. I walk on the "3" (of 10) position of the incline but drop it to zero to run. I really feel the pain in my calves the next day if I try to run on an incline
Usually I do 2 miles in 25 minutes every other day, though I've had a particularly bad TOM this week and haven't hopped on since Wednesday :/