To start, I love this watch.  It does everything I want a watch to do and does so rather well.  The countdown timer in particular is completely invaluable to me, and I use it on a daily basis.

The compass and thermometer are both pretty much gimmicks.  The compass is accurate for the first month or so after it's been synchronized, but can then be up to 90 degrees off-axis - not good.  The thermometer is against your wrist and only provides an accurate reading if you take the watch off and set it down for 30 minutes - not real useful for me.

Still, the world time and countdown timers are very compelling features and work well.