Strengths: Gives you speed and distance that you would not otherwise have.
Weaknesses: Looses signal too often making you think the batteries need changing. I have the the model without heart rate but does the same for speed and distance so assume the same problems as others. It claims that the batteries last for 1 hour every day of the year but I have got nowhere near that.
Overall: Unless there is a better affordable device then it is ok but can be a bit frustarting at times when you are in a race and it looses signal.