Strengths: Good functionality and good reliability. Time- or HR-based intervals are useful training aids. The coded transmitter is handy in a race (where other HRMs could potentially give intereferance). Battery life seems good, and the battery can be changed by the user in the Wearlink transmitter (which is also very comfortable). Being able to download your workout to a PC is useful if you're anal about analysing your performance like I am :-) The acoustic data transfer works surprisingly well - you just need to place the HRM very close to your PC's microphone (and most PCs do provide for a mic to be connected).
Weaknesses: This HRM stores only 120 HR readings, with increasingly long intervals between them the longer your workout is. E.g. only one reading per minute is stored during a run of between 1 and 2 hours, or every 4 minutes for a run over 2-4 hours. This can cause a problem if you (a) regualarly do workouts of longer durations, and (b) upload the data to your PC for later analysis. The HR data is only stored for the most recent workout. If you cannot get to your PC to upload teh data after a workout and then use your HRM again, you will only be left with summary data (HRav, HRmax, lap data) on the watch, and you will have to enter this manually into the PC softwear. Setting up interval workouts are a bit fiddly, whether you are doing this on the HRM itself or on the PC software (for later download to the HRM). The OwnIndex feature is a bit of a gimmick. Polar HRMs are a bit pricey, though you can be sure that their products are of good quality.
Overall: A good quality, reliable HRM, though you have to pay for the quality. Provides useful feedback on your workouts in realtime and for subsequent analysis, but those doing longer runs may find the limited data retention a limitation, in which case the next model up may be a better proposition.