In reply to gleaney:
I've also got a 610 but that came about after a lot of checking internet reviews and speaking to people. Have to warn you it isn't cheap but I've found its really improved my running. The only issue I've had with it is that the back panel has rusted badly.
This is NOT me but take a look at
http://connect.garmin.com/activity/193555993 for the sorts of things the 610 can record and analyse.
This guy completely rocks
http://www.dcrainmaker.com/p/product-reviews.html
With quality reviews of all? of Garmin's Forerunner watches.
I have no idea what your budget is or what sort of running you do but one piece of advice I will give is that you should stay away from the Garmin Forerunner 405 the one with the touch bezel. It might be on sale cheap but I used one and it was a dog.