Good comparison article here:
Garmin Edge 200 GPS Computer - First Ride Review | Cyclingnews.com
Here's why I wouldn't get one. Big reason, too limited on the displays. But that's also a selling point for them and why they say it's geared towards "recreational" cyclists. I love being able to customize my screens. I currently have 3 screens set up on my 500 with 5 to 7 pieces of information on each. As I love climbing and routes with big climbs, I have one screen that is dedicated to climbing with total ascent, current altitude, climbing speed, % grade, heart rate, and trip distance. This screen was my go-to screen for information and motivation during the Ride of the Immortals.
Also, the lack of compatibility with speed/cadence sensors and HR monitors is a big turn-off for serious training. This means not only can you not see your HR, but you can't see speed or cadence while on a trainer/rollers.
By the way, Nashbar fairly regularly runs 15% off and sometimes $50 off purchases. I picked up my Edge 500 for $200 during one of their $50 off sales.