*istD & low light

[Simon King]

Hi All,
I'm wondering what experiences people have had shooting, specifically
with the *istD, in low light around the 4-7 EV range. I'm interested in
how it effects the capture on the sensor, not focusing. 
Does the dynamic range stay the same? Are there other problems that come
up? Is it better than film at an equivalent ISO?
Also, has anyone experimented with long exposures of over a minute?
Sorry if these questions have come up before, and thanks in advance for
replies.
Cheers,
Simon