Strengths: Easy to read display. It's gives me that kick up the backside to keep my pace up, or to slow down if I'm going too fast on a training run.
Weaknesses: I do seem to have a problem locking onto the satellite signal sometimes. I'm a bit on the short side, and convinced this is due to my height!! At the beginning of the Reading Half Marathon last year I had to walk about with my wrist way above my head to get a signal lock :o), and if I run in a tight crowd then it can lose signal too.
Overall: It's a great training tool, and fantstic when you're racing. Would be lost without it!