Here is the thing: hybrids do not provide substantial fuel economy and environmental impact gains for people driving long highway commutes. It works very well in a frequent stop-and-go driving situation. While Toyota put the Prius on the market, GM spent their time developing a 2-mode hybrid bus providing both a boost in efficiency and comfort. When the bus leaves a stop, it relies on the electric motor while slowly ramping up the natural gas diesel engine. These buses have replace the fleet of tour buses at Yosemite National Park, where tour guides have reported seeing more wildlife on tours as these buses do not produce as much noise as previous buses, hence not scaring the animals away.
FYI, in GMC's booth at the NAIAS today is the 2-mode hybrid Yukon. This is due out in 2008.
Toyota may have beaten Detroit to the consumer hybrid table, but their days of dominance in this field is numbered. GM alone will, as of 2008, have a hybrid sedan (Aura Green Line), hybrid crossover SUV (Vue Green Line), and full size truck SUV (hybrid Tahoe/Yukon/Silverado/Sierra). That means you can drive a hybrid that actually looks like a regular car (imagine that!) instead of a poorly executed fashion statement.