I absolutely love the level of control the RS200 has allowed me. I now have the ability to know exactly how hard I'm working.
Things I found helpful:
The 'heart touch' feature... when you are running you can bring the watch up to the chest strap and it will either turn the back light on, or change to one of the other 3 display options so you can see different info (calories, time of day, etc, etc)
The exercise log is amazing, it really gives you a nice idea of what you've been up to. I use it in conjunction with the free training log @ www.mapmyrun.com
The OwnIndex feature is really nice to gauge improvement. I've had the watch for about a month now and have been intrigued to watch my improvement.
I picked the red watch, I think it looks very sharp!
The watch is bigger, if you are used to a regular running watch, but by no means it is too big. I have about average sized women's wrist and it fits nicely!