After 800 kilometres -- I've lost a bit of weight - my running paces are much the same as they were 6 months ago - I don't really know that I am fitter than I was 6 months ago.
BUT - my running has become a habit - and I don't even think twice now about running distances up to 10 Klm. I think that my HR rates have dropped a little ( but that might just be giving up coffee?) - I can stand on one leg with perfect balance.
I am happy enough with that though