Generally once you start to get into the 12-15 rep range and above, it starts to become an endurance exercise more than anything. Needless to say I do do high rep work here and there, and with my ab work is generally high rep. Not that its necessarily a bad thing, just don't expect to get much hypertrophy from it since the weight isn't heavy enough to really stimulate the muscle fibers into growth. You'll get some sure, because something is better than nothing, but optimal is generally around 6-8 reps, some people can also go up to 10 for hypertrophy. People are different though, they respond to different stimulus and different rep ranges, so I say find what works for you. Nothing is really set in stone, so go out and experiment and find whats best for you.
As for the Body-For-Life program, haven't really heard too much about it to really give an opinion, but the pyramid down, IMO, can be better done by pyramiding up, then down. For example. Say bench, do like 165 for 5, 185 for 5, 200 for 5, 200 for 5, 185 for 5...etc. You're peaking around the middle of the work sets, instead of pyramiding all the way up in the weight, where you're too tired to perform efficiently.
Good luck with the program man, or whatever it is you may do. Hit the weights hard!
Jay