VIDEO: Five Things About Hybrid Cars That You Should Know

are hybrids better or worse for the environment when the effects of production/disposing of all materials [batteries] are considered relative to improved mileage?

The Insight is not a "Mild Hybrid", nor are any of Honda's other hybrids. Honda's IMA system provides substantial motive power and is best characterized as a "parallel" or "assist" hybrid. It uses a high-power motor (replacing the flywheel) and a high-voltage electrical system.
Compare with GM's older Belt-Alternator-Starter syetem (e.g. on older models of the Vue Green line), which *is* an example of a "mild" hybrid, because it provides only very limited assistance to the motor and primarily just allows engine start/stop. The BAS system also uses a lower-voltage (48 volt) electrical system compared with IMA or HSD-type hybrids.
By the way, I have a 2007 Toyota Prius (NHW20) in that exact color, which I paid $13500 for recently (thanks to everyone thinking that the Prius was going to kill them at the time). I love it. The power-split (HSD-type) hybrid system *is* superior to IMA, both in terms of mechanical complexity (IMA also has a traditional transmission in addition to the hybrid system; HSD replaces the transmission) and efficiency. But it's not fair to say that IMA is a "mild hybrid" system, and the performance of Honda's IMA hybrids is vastly superior to actual mild hybrids and decently close to HSD-type hybrids.

@Brian: Definitions of hybrid types are not altogether accepted, so that's a challenging topic, but I'm afraid I have to disagree with you.
The motors in Honda IMA systems are either 10 or 15 kilowatts. I have driven most of them and have never once been able to make a Honda hybrid accelerate solely on electric power. The 2010 Insight is said to be able to do so under a very, very limited set of circumstances, but no one I have spoken to has experienced it.