A brilliant bit of kit. Does what it does perfectly - every time. Never crashes, never turns off mid ride and never fails to record. The battery on mine lasts ages even after years of use.
However, it doesn't do power or heart rate and the big one for me (which eventually forced me to upgrade), is that it doesn't download directly to Strava/Garmin Connect via Bluetooth. You have to plug it into a computer to download anything from it.
Navigation wise, it uses what is called breadcrumb trail. You plot a route and send it to the device, which provides a single line for you to follow on the screen - but no map. This works extremely well. I've now upgraded to a Garmin 520, which includes maps in the navigation. Having got used to not having maps on the 200, having the map adds very, very little.
I've only had the 520 a few weeks, and it has already had issues with freezing/failing to boot up, which took me about an hour to sort before heading out (thank goodness for youtube!). I miss the 200, but wouldn't be without being able to download activities via Bluetooth.