Strengths: It's getting cheap, from around £150 now which makes it a bargain. I've had mine for 4 months, it's great as (1) a motivator - getting me out running, (2) an assessor - letting me review my performance km by km (3) a trainer - helping me to run according to heart rate, keeping an accurate record of any distance.
No issues with any reliability, signal pick-up, or errant recordings.
Great to use on a bicycle as well.
And finally, if you can find a big space you can run around and make pretty patterns. With a bit of practice you can write words with it.
Weaknesses: Battery life of 11 hours is a little short for long cycling/walking trips.
Software is a bit rubbish - though Sporttracks is great (and free).
Overall: 10/10 - worth every penny. Maybe it's kind of sad to be so impressed with a gizmo, but I do like it a lot.