Actually, they are both good and bad.
First, let me start with the bad.
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The worst part is that they are not the 'silver http://www.blogger.com/img/blank.gifbullet' for an environmentally sound car. The fact is they actually do not buy that much in terms of fuel economy. The hero of the hybrid cars is so far the Toyota Prius, which granted is an economical car. But if it was not a hybrid it would still be economical. Actually, under some conditions, it would more if they took out the hybrid system.
See:
The London Times test against a BMW 5 series 520D
Hyundai I30 beats Toyota Prius in fuel economy / low emissions race.
In stop start traffic, the Prius is quite competitive, but on a long run it is not. Generally, with a mix of stop start traffic, whahttp://www.blogger.com/img/blank.gift would have otherwise been a very economical car, is even more economical. But is it not economical because it is a hybrid, it is just slightly more economical because it is a hybrid.
But what about cars like the Lexus, LS600h, whihttp://www.blogger.com/img/blank.gifch is not an economical car before it gets the hybrid treatment? Well, the answer is, even though it is a hybrid, it not economical.
See:
Comparison by Lexus enthusiast, Audi goes 50% further each gallon.
Audi A8: 31.5 MPG on test vs Lexus LS600h: 19.4 MPG.
Despite the rather woeful fuel economy, the LS600h actually qualifies for special concessions as an economical car! Not because it is actually economic, which it clearly is not, but simply because it is a hybrid.
So the negative is, these 'regenerative hybrids' as simply not that economical, and can even be very uneconomical. The technology is not 'game changing' as in the end all of the power, even the electrical power, is still generated as a result of gasoline in an internal combustion engine.
It has been pointed out that the production of the batteries can make these cars a very unsound environmental proposition, but this is somewhat an implementation problem rather that a fault of the idea. The problem is the idea is just not that good.
So why do people buy these cars?
Answer: Misplaced moral superiority.
Even if the car is really not that economical, you would think that hybrids alone could save the planet. People driving hybrids sometimes seem to feel they are doing their bit for the planet that everyone else is destroying.
OK- so is there anything good about these cars?
Answer: Yes, environmental consciousness!
Even if the whole 'superiority' thing is a bit annoying (especially when it can be completely misplaced) at least the whole question of economy and emissions has been taken to a whole new level and been made into a selling feature.
