The very first run I ever recorded with my Garmin 405 was last years last long run leading up to my first half marathon on July 5 2009.
So it is interesting to make a comparison:
This years run http://connect.garmin.com/activity/38264066
Last years run http://connect.garmin.com/activity/7799277
Both were 1hr 30 min duration. In last years run I believe I was fastidious about warm up so started with a heart rate at around 145 or so for the first 1km split. I did 18.13km in 1:29:52, and according to what I blogged about it, I was fading badly toward the end. In the run it self, I was doing faster splits in the middle but lost all pace at 17 km.
Av HR this year 137 last year 157. Even counting the fact that I warmed up properly before the run last year that is a massive difference. The biggest difference was the even pace this year and no fade what so ever. And this years run was over a hilly course, whereas last year it was almost completely flat.
Even if my marathon race on 4 July is a massive stuff up and meltdown, I have made a huge improvement in fitness overall this year.