I’ve been a satisfied owner of a D100 for about six months and have had Nikon film cameras for a number of years. I can’t offer anything on the S2 but here are a few thoughts on the D100, concentrating on things that aren’t necessarily obvious from the specs.
In the hand, the D100 feels most like an N80. Lightweight, not fragile, but not industrial strength either. I tend to be easy on my equipment and I haven’t had any worries or problems with durability. The controls will feel familiar if you are familiar with Nikon film cameras. The ability to customize control functions is great. The camera feels very responsive.
One consequence of a less than full frame sensor is that the viewfinder has to match it, resulting in a viewfinder that feels a little dark and cramped relative to Nikon pro film cameras. AF performance is good—not blazingly fast but okay. I have turned off the annoying white AF assist light and rely on IR AF assist from a speedlight in dark situations.
Image quality is terrific. I’m thrilled with how good the images are. No noise. Good color, contrast and detail. The fast ISO speeds are very helpful to me. I have decided to keep a ND filter in the bag in case I have any situation that needs wide aperture and slow shutter speed (e.g., a need to use fill flash in brightly lit conditions with maximum flash sync of 1/180).
I shoot RAW mode exclusively. Without post processing, images will often appear a little flat and underexposed. I think the slight “underexposure” is actually keeping the highlights from blowing out. Post processing makes all the difference. Nikon Capture software seems to work well and integrates well with Photoshop. There is a huge amount of detail in the shadows of D100 files and it is very easy to bring it out with the Capture software.
If you have older (non-AF) lenses, make sure you check compatibility. Not all lenses will meter with the D100.
You probably know that Nikon digital cameras require the DX speedlights for TTL flash; manual and auto flash (non-TTL) work okay with SB-26. SB-28, etc. I have the SB-80DX and it works great. Be aware that digital TTL requires a pre-flash to measure exposure. This essentially negates TTL mode with optically slaved use or multi flash setups. Manual and auto mode are available however for these purposes.
Battery life is great. I have the battery pack/grip, but even a single battery lasts a long time.
You’ve probably heard about the need to clean the sensor occasionally. It’s true, but not a big deal. Once you have the supplies and have done it once, there’s no problem. I am careful about trying to minimize dust getting in when I change lenses. I think I have cleaned the sensor three or four times since I got the camera. Some people may have to clean more frequently, particularly with heavy use.
The rear LCD viewscreen is great; I use the histogram all the time to check exposures. Glare can be a problem using the LCD screen however.
For your type of shooting (wildlife and wedding receptions anyway) you ought to be aware of buffer size. The number of frames you can shoot in burst mode depends on the image format you choose and whether you have noise reduction turned on. I don’t know how it compares with the S2, but it is definitely something you have to be aware of. You can’t just fire off 8 shots on motor drive while the bride is throwing her bouquet, for example. For landscapes, which are mainly what I do, this isn’t an issue. For landscape shots, two things I have found that work very well are the noise reduction and the mirror pre-fire, which is the functional equivalent of mirror lockup.
Hope this helps.