What's missing compared to the D70 and D70s that I'd miss a little:
1.) No White Balance fine-tuning. You can do this through bracketing, but that's cumbersome. If you care about this as I do get the D70s; 99% of people will never miss this.
2.) No front (secondary) command dial. That's OK, the D50 also lacks the WB fine tuning you adjusted with this dial. To adjust the aperture in manual exposure you hold the aperture button (same as the exposure compensation button) while turning the command dial. I prefer this in A and S modes since I never can remember which knob to turn on my D70; on the D50 it's always the one command dial that does it.
3.) No ability to use the built-in flash for remote control of external flash. To do this you'd need to buy an SU-800 or SB-800 for a few hundred dollars, which makes no sense. If you use this feature (I do) just get a D70 or D70s. I have a whole page explaining this here.
4.) No viewfinder grid. I would miss this, most people won't.
5.) SD vs. CF memory cards. Again, better for a tyro whose point-and-shoot probably took these. Bad for pros since we all have pockets full of CF cards, in fact, for a pro the price difference between the D50 and D70s is about the price of a few new SD cards.
6.) No ability to set the lowest shutter speed used with flash in P and A modes. I do set my camera to 1/15 or 1/8 instead of the usual defaults of about 1/60.
7.) No AF area selector lock button. I rarely use this and it bugs me when I do, so no big deal.
8.) Won't work with MS-D70 battery holder for disposable CR2 batteries. Even though the D50 uses the same EN-EL3 rechargeable, there is a pin on the MS-D70 that corresponds to a hole in the D70 and D70s. To jam it into the D50 you'd have to take a pair of dykes to the MS-D70, but don't do that since the MS-D70 puts out a higher voltage than the EN-EL3 for which the D70 and D70s can compensate and the D50 can't. The EN-EL3 makes 7.4V while the MS-D70 pumps out 9V. I do keep an MS-D70 in my bag if my rechargeable ever dies on me, which has never happened in over a year of use.
9.) 2.5 FPS compared to D70's and D70s' 3 FPS.
10.) No prophylactic LCD cover. I suggest using a conventional stick-on one cut to size like these here so you simply may replace the cover, and not the camera, when you scratch it up.
11.) No illumination of top numeric LCD panel. In the dark use the menus and see them on the rear color LCD.
12.) No depth-of-field preview button. No big deal, 99% of photographers don't even know what this button does even if the D50 had it.
13.) No two-finger FORMAT CARD buttons. You have to go into a menu. Pros refoprmat a card every time they use it. We don't just erase the images. We reformat because it eliminates any potential for data errors and other weird things that can accumulate over time without reformatting.
What's missing that I never used on my D70 anyway:
1.) Only 1/4,000 top shutter speed compared to 1/8,000. Not important; I've never even used 1/4,000 on any of my cameras.
2.) The D50 loses the hard button for bracketing. One has to use a menu instead.
3.) No custom function for setting exposure compensation without having to press the +/- button. No big deal, the default is just hold the +/- button and turn the command dial like every other Nikon DSLR.
4.) No ability to change the diameter of the center weighted meter (Note to Nikon: specs on page 130 claim this feature however there is no way to set it in the menus on page 96).
5.) No ability to set the order of bracketing.
6.) No ability to allow your selection of AF areas to wrap around when you go off one end.
7.) No ability to turn off the "use flash" symbol in the viewfinder.
8.) No meter mode button. I never use center or spot meters, but if you do you now have to go find them in a menu. The meter button of the D70 and D70s is now the self timer and remote control button on the D50, which I prefer.