Strengths: I used it properly for the first time at the Great Cumbria Run this year and the mile markers were spot on 1 mile apart. It even indiated i'd started it off to soon as i was 0.11 miles further on than every mile marker.
Weaknesses: Calorie counting is dubious, claimed i'd used 2600 calories at the GCR where as i had used more like 1700.
Altitude/elevation is not accurate, when stood still it was jumping around by upto 50 foot at times.
Overall: Overall its a very good watch if a little expensive. Yes the Garmin's maps are rubbish but if you use SportTracks it not only corrects the dodg calories but gives you very nice maps.
Just loaded the GCR log onto SportTracks and the information is very impressive.
This watch when coupled with decent software is excellent.