Hey,
I was at the Apple Company Store a few days ago, and I recall them saying that the AirPort Extreme base station doesn't inherantly have a larger range (for that you'll need the antennas + the antenna version of the APBS, ~$50 more).
I'd assume that "60% reception" means "60% of the theoretical max this base station can put out." not sure, tho. And yes, lower speed = higher ping.
I bought the "graphite" APBS (v1.0) in late 1999 or something, and i think it was $299. The Extreme base station is $199. Good buy--i don't see why you'd ever get the graphite or snow base station.
Last, I'd assume that the 802.11b/g signal doesn't do any physical harm, otherwise we'd be seeing a ton of hospitalizations around the world

. I mean, think about what your radio does...it just picks up signals floating around the air; radio doesn't
harm anyone...
hope this helps. sorry for the wordy explanations.