Most of my photographic work is in the field of nature and
wildlife. This includes many low light pre-dawn and post-sunset
shots. I am considering purchasing a D1X. A friend and college
professer of photography told me that one of the major drawbacks to
digital photography is the inability to work in low light
conditions. Is this true? Any help or advise on this subject would
be appreciated.
Nonsense. First of all, "inability" is an awful strong word. My dictionary equates this with "complete failure." Since I use my D1x all the time for exactly the type of photography you say you do, I'd have to say that your professor friend hasn't actually tried what he states is impossible.
Yes, there are some issues you'll have to deal with. In hot climates, dark current can be a problem with long exposures. At the more likely cooler temperatures you're going to encounter you're not likely to see any additional noise out to about 5 second exposures, and it's still reasonably well controlled at 30 seconds. I'd recommend that you shoot a second "lens cap frame" at the same shutter speed for any exposure over 1 second, though, as this can be used a noise baseline you can subtract in Photoshop to slightly improve your results.
If you shoot NEF, you can often "push" exposures by as much as two stops after the fact. Some argue that you get less noise this way, some argue that you get more (I'm in the latter camp, especially if you use Bibble or QImage at the 10mp resolution). You also should note that you don't have to worry about reciprocity on long exposures--the camera is accurate down to the limits of its exposure meter (EV 0).
In short, don't be afraid of the dark. --Thom Hoganauthor, Nikon Field Guideauthor, Nikon Flash Guideauthor, Complete Guide to the Nikon D1, D1h, & D1xwww.bythom.com
