The battery being replaced every year thing sounded different from everything I've heard about hybrids, so I looked it up:
http://www.hybridcars.com/faq.html#battery
"The hybrid battery packs are designed to last for the lifetime of the vehicle, somewhere between 150,000 and 200,000 miles. The warranty covers the batteries for between eight and ten years, depending on the car maker. Some detractors doubt that the batteries will truly last that long, so only time will tell. "
Some time ago I read that replacement batteries would cost 30,000 dollars. More recently it was $3000. The faq you linked to dances around replacement cost, so I suspect it's a killer.