A lot to learn, but break it into manageable pieces
The recent Nikon DSLRs--the D300 and D3 in particular--seem to have pushed a number of hold-out film SLR users into the digital world. The number of film-to-digital transition questions I've been getting for the past six months is actually as high as it's ever been, even back to the early D1 days. The introduction of the D700 is going to push a few more into the fray, so I thought it wise to make a few comments.
Negatives or Slides?
If you shot negative film, you're probably going to find out you're not as good as you thought you were. That's because negative print processing at labs has been "magic" for a couple of decades now. Indeed, current lab machines do all kinds of elaborate analysis and correction to the data they obtain from the film negative. And because negative film has a pretty broad exposure latitude to it (measured in several stops; most negative films can produce good prints across a range of at least three stops, and usually more), you can actually miss the exposure by a lot and still get back very nice prints.
Digital is more akin to slide film. Miss the exposure and you'll get less-than-perfect prints. Like slide film, digital cameras simply don't like overexposure. On slide film, things that are too bright simply produce clear acetate. With digital, things that are too bright produce no ink on the paper (there's no such thing as white ink in most digital print technologies). Both are not so great consequences of overexposure. Meanwhile, underexposure tends to produce muddy shadow detail in both slide film and digital exposures (especially if you're using digital printing techniques with film). Grain can become more apparent on film, noise more apparent with digital. So, with slide film and digital the rule is "optimal print results require optimal exposure."
So, first transition problem: shooting negative film may have been masking the fact that you haven't been achieving optimal exposures. First and foremost, make sure you can nail exposures.
Most of the film holdouts now transitioning are still using what I'd call non-modern SLR bodies. Those would be FM2, FE, EM, FA, FM, FM2n, F, F2, F3, and a host of other the all-manual SLRs Nikon produced from 1959 until the "electronic" cameras started to appear in 1985 and culminated in the new automatic era with the F4 introduction in 1988. Even the N8008s, N90s, and F4 that carried Nikon through the late eighties and early nineties are still very simple in design compared to what the F5 unleased, and which the Nikon DSLR line has now taken to the extreme.
Thus, transitioners have another issue: they have to learn completely new camera and shooting controls and techniques, plus they have to learn about how digital is different than film. I've got two words of advice to these folk: go manual. Forget trying to learn the complexities of the camera for a bit. Set manual exposure and manual focus and get the shooting differences as much out of the way as possible. Shoot the camera like you're used to. Spend your initial energy learning about the decisions you have to make to optimize the digital side of the equation (white balance, picture controls, image quality, Color Space, etc.). And even some of those can be simplified (shoot NEF+JPEG and set the Color Space to sRGB until you know how you want to control the digital side). In short, put your initial energy into the digital differences, not the camera differences. This makes the problem more like finding out about how a new, slightly elaborate, film stock impacts your shooting.
Only once you've mastered the digital side of the equation should you start looking at all those modern SLR goodies Nikon has stuck into your camera: autofocus, super sophisticated metering, wireless flash, Live View, and so on. And my advice there is to take one subsystem at a time and master it. Don't try to turn all the goodies on simultaneously, you'll get overwhelmed. One. Subsystem. At. A. Time.
Everything's the Same.
Look for the similarities. With film, we had to clean the negative or slide before printing. Guess what, we now have to clean the sensor. Nothing's changed fundamentally, only the location and equipment we use is a bit different. Exposure is still exposure, and mid-tones are still mid-tones. All of Ansel Adams' Zone System can certainly be applied to exposure still, you just won't be in a dark room making some of the adjustments (hint: if you need Zone I or Zone X you may need to use HDR techniques to "develop" them). Lenses still work the same way (at least for FX ;~).
The list of similarities you'll develop will eventually be long. True, the actual widget you toggle, turn, or push to make an adjustment probably is quite different or located in a new place, but you still control the same variables as before (shutter speed, aperture, ISO, exposure compensation) plus some new ones (white balance, picture controls, color space, frame rates, exposure modes, focus modes, flash modes, and so on). Start by finding out where your cheese was moved (e.g. "what controls the shutter speed now if there's no dial for it?") and then add the new stuff later.
Enjoy the Control
One thing the digital revolution did is give us back our darkrooms (Photoshop, et.al.). It also let us (kind of) design our own film. A US$999 DSLR coupled with some good software and a monitor calibrator and a US$500 printer gives you full control over everything from capture to final 13x19" print. FULL control. As in "if it ain't right in the print you did something wrong." As some of you may surmise, I'm a closet control freak. Give me the power to do my own thing and I do. So I jumped on digital as far back as the early 1990's, starting with scanners and printers, but eventually opting to go 100% digital. I've put my time into the wet darkroom of the film days. I've processed just about everything except Kodachrome, and printed everything. Let me tell you, digital is ultimately not only easier, but gives you a finer degree of repeatable control.