the charts are ok, but you cant easily do week over week comparisons. polar has some clunky software that goes with their nicer heart rate monitors.
http://www.pursuit-performance.com.au/polar/html/segments/products/PPP3/support.html
It might give some good ideas of the kinds of charts/comparisons/features that would be great to have. I'll send you some screenshots so you know what I'm talking about.