Your GM brother-in-law is out of touch.
My '05 Prius has a guarantee (non-pro-rated) on the entire
electrical system, including the batteries, for 120,000 miles or ten
Last I heard, GM was pushing hydrogen.
My guess is that my Prius battery will be at the end of its warranty
before GM sells you a hydrogen-powered vehicle.
Read the latest (April, '05) Scientific American about current
progress on hydrogen-fueled cars. There are humungous problems
still to be solved before it becomes really practical. They say it
could be between ten and 50 years before it is economically feasible.
Many other posters have already replied. All I want to say is the your
brother-in-laws does not know a thing about the Prius. You should do
your own research instead of believing all those lies. Since he is a
GM mechanic, he may have a hidden agenda.