I got this because I got sick of my Android smartphone's GPS being off by as much as 0.5 miles in a 4.25 mile run. The Garmin Forerunner watches all got excellent reviews, and I went with the 210 just for the interval function. It works just as well as I hoped.
*very accurate - generally within 0.01 miles for me
*lightweight - I barely notice that it's on my wrist, in comparison to my brick of a smartphone
*easy to use - both the watch itself and the Garmin Connect website are a piece of cake to use. Even better,it's very easy to export the info as GPX files for import into your favorite run tracking site, if you don't want to lose your history.
*not truly waterproof, I tend to be a bit paranoid about dunking it
*can't see current GPS coordinates - would be nice to just have one device to use for both running and finding a trailhead
*it takes about a minute or so to lock onto satellites initially, so it's not quite as simple as strap it on, step out your door, and start running