Strengths: Hmmm...I've nearly always run in these because they are so comfortable straight out of the box and I've avoided injury over the 5 years or so I've been running except when wearing a different make! However...
Weaknesses: ...this new model seems far more uncomfortable. Still no injury (so pleased about that), but they don't feel right. At the start, I thought it was because they were new, but I'm 120 miles in now and they still feel odd. Left shoe especially feels like the sole has an edge inside which my two outer toes hang over and gradually get pins and needles. Think it is settling down, but I'm not impressed with this new model. Feel less flexible than before, as well.
Overall: After being a fan for several years, I'm disappointed with this model.
'THIS REALLY DOES IMPROVE YOUR TRAINING (AND GET YOU HOME)'
Strengths: For me, this little device improves every different type of training I do. It keeps me at the right (slower) pace on long runs, it helps me keep my heart rate at the right level for tempo runs and it (fairly) accurately measures intervals for speed work. Not only that, but when running in a new place and suddenly lost, you can pull up a "snail trail" of your route and work out where "home" must be (I have done this in the Channel Islands). Finally, it is easy to take off and leave at home when you want to "run free" and not be tied to a schedule/pace/heart rate.
It's good that you can transfer all your run data onto the PC. Even better now that MotionBased is properly involved (the basic Training Centre software is rather basic).
Weaknesses: Sometimes, it can take a long time to lock on to the satellite signals. The USB connection to the PC on mine has become a bit flaky - sometimes it just won't read data into the PC and needs a lot of jiggling around or a PC re-boot. The Training Centre software is not very flexible.
Overall: This really does make a difference to my training. And the geek in me can upload the data to my PC and look at it in Traiing Centre, at MotionBased or through Google Earth - all in fairly easy steps. I train far more intelligently with the strapped to my wrist, so for me, it is money well spent (although it was quite pricey when I bought it).