Strengths: small and light, easy to run with. The cheapest running watch that includes distance monitoring. Nice community feel to the nike website
Weaknesses: Nike website & run graphs are buggy. Can be difficult to get calibrated. No backlight.
Overall: GPS watches are more accurate, but then they are quite a bit more expensive. At the time of writing you need to sign yourself up to either runnerplus.com or slowgeek.com for decent run graphs, but once you do this is a valuable training aid.