My heart will go on - the benefits of running with a heart monitor/belt

On opening the wrapping on my first garmin watch (best Christmas present ever!) I also noticed this type of belt marked heart monitor amongst the packaging. At that point in my running life, a watch that measured miles and speed was enough technological sophistication for me, this heart monitor was just too much.
During my training programme this time around and using the benefits of the myzone belt, I am beginning to realise how wrong I was to cast aside the heart monitor previously and how beneficial it has now become to me - especially on long runs.
Upon checking on my heart rate I can now see if I'm running at the correct intensity over these long runs - a high heart rate at the start of the run is unsustainable and will result in burnout and a very tough finish. Looking back over these runs and getting to grips with running at my optimal heart rate for these long runs enables me to get used to pacing and ensuring that the tank isn't emptied early on and the last few miles are as bearable as the first and the long runs and marathon itself prove to be a positive (maybe even enjoyable) experience.