Great job! I've been dipping in and out of this programme for a while. I keep having to take breaks from it because I have feet issues, but it's hugely motivating and fun. Back on it now, @ week 4.
I always sucked at running - was actually given running as HOMEWORK for gym class when I was a kid! - and am pleased as punch at being able to do it now. Also love that running is free!
Check out Runner's World
for great tips. I agree with those suggesting to stick at a given week if at any point you find it hard going - takes a while for your feet/calves/knees to get used to it.
Also would say (from my experience of various injuries) to avoid going harder than the programme advises; make sure you have good shoes (see RW for advice on that); switch up terrain to prevent overuse injuries - run on concrete as little as poss, if you can; and check form (at eg RW, again). Oh yeah and running outside is more difficult than the treadmill - no shame in staying on the mill for a while (if you do want to run outside, I'd go back a week). And strength training on off days can help with joints too.
Awesome, happy running!