I was going to further demonstrate what Juergen talks about.
Here is a timelapse I shot from my balcony, with the D200's built-in timer and with everything Auto.
Especially the transitions are troublesome, when the camera has to decide between two neighboring exposures. Which seem to be too far apart.
What a real timelapse feature needs is
temporal dampening. You'd need to remember the last exposure time, then determine the new Auto-Exposure. If the new Auto-Exposure different by a threshold (like 1/4 stop), then change the exposure in that direction, but ONLY by 1/32 stop. Of course, both thresholds should be configurable. It doesn't really matter if we're lagging behind the AutoExposure, in fact that may actually be a pleasing effect.
For now, I treated the sequence above with timeblend in After Effects. This sort of shows what I would like to see in the sky, but unfortunately is also kills some of the more interesting things going on in the citylight windows and elsewhere....
Nothing that couldn't be fixed with keying and compositing, but this added effort only pays off for when I really need to use that footage for something... Would be better if it came clean from the camera in the first place.