Strengths: Once it acquires the signal, it sticks to it like glue, extremely accurate, nicer to wear than 301 and 101, sampling rate much higher than these models. Heart rate monitor is comfortable to wear. Interesting touches like the compass and satellite graphics.
[Update 10/12/06] Update (Nov 2006) to my previous comments and posibly an aid to those finding it slow to acquire the satellites. Simply take it off and put it on a stationary object like a car roof or a wall, I guarantee it gets the signal in under a minute every time. Update 2 (Dec 2006), the firmware and software upgrades have made it even better, I have purposely tried to hinder it during initial locking on by moving around but it locks on quickly regardless. What other people are experiencing genuinely baffles me. Calorie calculation now reasonable.
Weaknesses: So accurate that it loses the signal temporarily under motorway underpasses - gets it back very quickly though. The calorie estimation is utterly farcical, the 301 and the 101 did that correctly using the well-accepted formulas to calculate this, why change it ? Also I liked the 301s heart rate autolearn feature.
Overall: I wouldn't run without it, absolutely essential training aid if like me you hate guesswork and subjective feedback. Don't pay UK prices, I paid about £180 all in on EBay.