I've been getting faster and mostly adding mileage. I missed one week due to back pain, but that's gone, so I'm happy.
Here is the data (I made a graph, but I can't get it to post!):
I started off pretty slowly, but have picked up speed as I've been riding this spring. My goal for the summer was to be able to reach 50 miles a week. I think I need to think of new goals. I'm quite pleased that I'm riding over 15 mph over an entire week, especially when I'm adding mileage. I'm already over 200 miles for the month of May. Not bad at all!