My 400M training was tough but I enjoyed them too. I had doubt a time or two on the speed I was trying to maintain, but was able to finish off pretty strong.
I am so addicted to running right now, I REALLY wanted to do more running this afternoon before we went swimming. Good thing I have my training plan, or I would be running way to much I'm sure!
I'm still using my Nike+ because it keeps me in touch with the running community I've used for support over the last year and a half.