The point about the S2
Pro batteries has already been addressed many times on dpreview and here. As a user of the S2
who very carefully weighed the options of the different Nikon-based DSLRs, the S2
Pro was the best choice. For me its battery set-up is one of the S2s advantages and a reason why I got it rather than the D100. All of my glass is Nikon so that ruled out the excellent Canon choices of DSLRs for me.
I for one avoid proprietary features on many things I purchase, especially when it comes to the batteries. When I travel with my camera for a job I may take 2000+ images. Having to find a place in a remote location of perhaps a foreign country, to plug in and charge my proprietary battery is not only inconvenient it is often impossible.
Yes I could buy extra proprietary cells, and pay lots of money or I can do what I have done and purchase several sets of excellent rechargable AA
(which also work in my flash, flashlight, radio etc.) and keep them in my bag. If I were to deplete all of those (I never have) I have the comforting thought that in an emergency I can buy AA
's just about anywhere.
As to the C123s the S2
also uses. The camera will work fine without them because I don't use the cameras built-in flash, but just to be safe I have a small pelican case with 12 spares inside. I bought them in bulk a year ago an have used six since then.
Most of the current selection of DSLRs are about even for image quality in my opinion, it comes down to the features you want and need. Do a little reading, look at sample images, count your money then make your selection. I'm sure whatever it is you will be satisfied with the end results.