You can play with the tool, it's online on my blog :)
I like it and think it's great for a getting this kind
of info quickly, but ...
I believe the using a code profiler (I use ants ...) and
analizing the results on an actual run, will give a
better understanding of which functions are the most
important to debug (called the most times, take longest
to process, etc ...).
Don't get me wrong, i'm not comparing one-man's work to
a known company's product , but monitoring an actual run
of a program will give you (i think) better results