Strengths: It offers everything you want in a training monitor (apart from an HRM, but this is the 201 not the 301!). Measure distance, pace, calories burned, altitude, and even backtrack along a route if you get lost.
Best of all, get home, attach it to your PC and analyse your training for hours afterwards. A real motivator to keep the logbook looking good.
The ability to race against a virtual partner on training runs or to pace you during a race is also a fantastic feature which I use a lot.
Other very useful features are the auto-lap and auto-pause features that mean you're not fumbling around to stop the clock during "pit-stops" and sometimes you can (dare I say it) ignore it during runs and look at your splits when you get home.
So many possibilities!
Weaknesses: Size can be burdensome. I find it okay once used to it, but my rather more slender wife likens it to wearing a brick on your wrist.
Lack of Apple Mac compatibility is a real drawback, but that is due to be resolved with the 205/305 so presumably this will flow down to the 201/301.
Can take a while to pick up a signal, but this is a good excuse to stretch before every run!
I personally don't run in wooded/covered or built up areas so have no problems with reception on the run.
Overall: A pretty much indispensible tool for beginners and wisened old racing snakes alike.