First of all, and most importantly (at least to me), enjoy the ride. The data can be fun while you ride and I think it's fascinating to look at the charts and numbers I get when I download my Garmin 800 into my home computer.
For me, it's a way to enjoy the ride all over again; after I've gotten home, had a shower, maybe gotten something to eat, and yes, I find it entertaining and occasionally enlightening. True, as someone noted it won't last for a 600 km brevet, or even a double century for that matter, but I'm sure that will come down the road somewhere, sometime.
Until then, I'll enjoy the rides, enjoy the data, and know that even though it's good for me, it may not be good for you.
Rick / OCRR
PS: If you're curious, here's a link to one of my rides that you can look at. And yes, it was a very enjoyable ride!
http://connect.garmin.com/activity/132753760