Dave
You need to decide on what features you want.
As an aside, only some tools automatically record your mile split i.e. without you have to press a button every mile.
I have been using a gps tool from timex which has been fine. However I recently decided I wanted a heart rate monitor as well, so without spending £150+ on a new combined tool, I got a hrm for under £40.
I am also getting the book
Heart monitor training for the compleat idiot by Parker. There have been a great number of recommendations for this book on these boards.
Oh I prefer the gps tool because with the footpod things, I think you need to have a constant stride length, especially going up/down hills, which I certainly don't.
But with the gps, if you lose the signal (i.e. in area with tall buildings/trees), then the distance measured and hence speed will be less than the true total. I can live with that as I know I have done as a minimum what is recorded on the monitor.