I recently got a Garmin Edge 305 with heart rate monitor.  I've done my commute a few times with it so far.  The data it collects is pretty astounding.  I haven't had much luck with the heart rate monitor so far.  I'm getting garbage readings from it.  I haven't swapped the battery in the chest strap transmitter yet so I'll try that next.

The best thing about this unit is what you can do with the data it collects.  The unit comes with some software that is fine for basic historical tracking.  The real action happens online at places like Motion Based.  There you can upload information from your rides and the site presents it with a really neat Google Maps mash-up.  Other cool stuff you can do is download rides either you or someone else has uploaded to the site and save it ot the Edge unit.  The unit then lets you use a mode that shows two riders so you can see how you are doing against the ride you stored on the unit.  You can race yourself or someone else virtually - pretty neat.

I also plan on taking it skiing next time I go just to see what the data looks like.

Once I get some more experience with this unit unber my belt, I'll write some more about it.