Pollution from cars in traffic at low speed is particularly bad for people, but a hybrid can spend much of that time running on battery only.
I can't disagree with you there. Hybrid cars (actually, fully electric cars) would be great for most if not all cities. (Screw it, just design cities without roads for cars and make people bike everywhere, that'd actually be a really cool social experiment.) However, I'm not talking about just city driving. Yes, a few MPG will add up over the years, but how long will it take you (using that few MPG) to pay off the extra money you used to buy the hybrid in the first place? If you're going to tell me that you bought the hybrid to help the environment, you're better off donating the extra money to research that aims to help reduce pollution.
Some simple, back of the envelope calculations. (All #s taken directly from honda's US site)
Honda Civic Hybrid Price: ~$24,500
Honda Civic Normal Price: ~$18,500
Hybrid Avg MPG: 45.5 (I averaged the highway and city MPG)
Normal Avg MPG: 34.5 (I averaged the highway and city MPG)
That extra $6000 will buy you 1500 gallons of gas at $4.00 per gallon.
Let's assume you drive 20,000 miles per year.
Hybrid gallons consumed per year: 439.6
Normal gallons consumed per year: 579.7
Difference: 140.1 gallons/year
To pay off that extra $6000, you'd have to drive for ~10 years (200,000 miles), assuming that the hybrid keeps it's high MPG its entire life (which, as we've seen, isn't true.) If you assume that you're JUST driving in the city, the #s aren't much better.
Also, 10 years is much longer that most people keep cars now-a-day.
Of course, the number above scales inversely with miles/year driven, so if you double that then the number of years will be reduced by half, but even if you drove 40,000 miles per year (which is a lot), it'd still take you 5 years (that's 200,000 miles on the car mind you) to pay it off.
If you'd repeat this calculation with a clean diesel, the results would point even more in the direction away from hybrids, especially since diesels CAN last a quarter of a million miles or more, whereas hybrids don't stand a chance.
The only way hybrids will ever be effective at reducing pollution is if you force everyone to buy them. I don't think big oil or most people (especially gun-toting, big truck driving, americans) would let that happen. (Since I'm from the US, and work with gun-toting, big truck driving americans I'm allowed to say that. And yes, we do refer to ourselves as "Americans.")