I've been using Speed once a week or so, and although I'm still VERY slow, I think it helps. Yesterday was HOT, so it was 9.30pm before I headed out. I planned to use Speed but I also wanted a bit of a longer workout, so this is what I did:
* warmup walk 5 minutes, no podcast
* started podcast and did a slow jog through the intro (ie the bit thats supposed to be the warmup walk)
* 5 minute jog then 9 minute intervals as per podcast
* slow jog through 5 minute cool down
* 5 minute walk home after podcast finished
It worked well. I was also pleasantly suprised I was still capable of a slow jog after the intervals.
Sharing in case anyone else finds it useful.