I've been mulling over whether to get one but mainly for the mapping.
General consensus is 500 is good with HRM, otherwise gor for 810 or an Edge Touring for all the bells and whistle. Check the Garmin thread out. Obsessive amounts of knowledge and handwringing there over which to buy.
That's the thing, I do want to get more into training harder and I'm a bit of a geek when it comes to stats - they tend to make me work harder
for example I wanted to get down to a certain weight and body fat % and did it as I was driven by the numbers
Plus surely everyone needs to know just how fast they can go, right?