Strengths: Very accurate speed and distance that also works on treadmills. Rates your current fitness/stress levels using a variety of methods. Can personalise heart rate band (low, low-medium, medium-high, high). I found this invaluable as an older runner starting off running. Gives feedback during exercise. Downloadable data to effective e-diary to follow progress by day, week, month or year. Can add personal notes on sleep, weather, and how you are feeling. Diary provides weekly bar graphs of progress. Ice-breaker at events!
Weaknesses: Need to read the instructions carefully to get the most out of it. Need a functional IR port on your computer.
Overall: This builds up into the ultimate in self-evaluation. Being able to review graphs of training runs and events is extremely motivating. It really helps you to think about your training so that you can optimise it.