Strengths: The RS200SD is very easy to set up and use. After calibration - which I preferred to do manually - the speed/distance function is pretty accurate. The real time pace display is invaluable for tempo runs and I plan to use it to pace my next marathon in Paris (is this cheating?).
The unit can be set to automatically record lap/split times. I have mine set to record times for each mile. Further information for each split includes average and maximum heart rate, average and maximum pace and distance covered.
The RS200 SD is also a great looking product and I am happy to use it as my main watch.
Weaknesses: Whilst the unit itself is almost flawless - we'll come back to the almost later - I have found that the wearlink belt supplied with the product can have problems supplying a steady signal to the wrist unit. This is very frustrating if you are trying to gauge your training run through heart rate. However, I have found that cleaning the belt thoroughly with soap and water after each use can minimise this problem.
The watch is also prone to freezing. This can easily be rectified by pressing all four buttons simultaneously, which resets the unit. Fortunately, most of the user setting are retained when this happens.
Overall: The RS200SD provides excellent value for money. It has all of the most useful functions of the more expensive - and less attractive S256X - and can be found on-line for under £130. What more could you ask for - a garmin perhaps??