I've been running with the Garmin FR220 for about a month now, and I love it. I went for the 220 rather than the 10 mostly for the battery life, and the ability to add a heart rate monitor and a foot pod (currently, I use neither). I also LOVE the fact that the run/walk timer (and other alerts) can vibrate and/or beep.
I also like being able to program workouts in the watch (via the Garmin Connect website), such as interval training, mile repeats, etc. But I was disappointed to realize that when you use the workouts, the run/walk timer doesn't kick in. Since I use the run/walk timer pretty exclusively, that makes the workouts feature less useful to me.
Also a word of warning: The Garmin Connect smartphone app doesn't work anywhere but iPhones (and I think only relatively new iPhones). I knew this before I bought the watch, and it wasn't a deal-breaker for me; I just upload my data through the USB cable via my laptop. But the Garmin marketing about the smartphone integration doesn't say that non-iPhone phones aren't supported yet, so this has been an unhappy surprise for some folks.