Brock,
My wife purchased the Toyota Prius because the Honda was not a practicle vehicle, 2 seater. If the Honda Civic hybrid had been out as it is now she would have gotten it. As it is the Prius has performed flawlessly for 4 months with no problems and has gotten 45 mpg consistently. That said, a european style deisel will get the same milage with well established technology and an expected engine life in the 100s of thousands of miles. The trade then becomes cleaner newer technology for dirtier mature technology.
As an aside, if the hybrid is purchased for business, as my wife did, the vehicle is granted TRIPPLE depreciation under current tax regs and can nearly pay for itself in taxes in under 3 years.