difficult decision. D70 has speed and feature set going for it. S2pro feels great in the hand and image quality cannot be beaten. both are compatible with a great range of nikkor lenses. think it boils down to usage. if you intend for use for portraits or close detail photography go with the S2Pro. if using the all around use or a backup, get the D70.
You can check out dpreview for your answers. If you can't understand most of the stuff, you probably wouldn't be needing a DLSR. Maybe wait a while more to see what S3pro has to offer and learn the basics for the time being.
S2 Pro is basically same as F80 in camera setting. So, there are B mode, 30s...etc. It has the extra of multiple exposure. It uses all SB speedlight (non DX also can), so you don't have to upgrade to new speedlight.
Whatever lens D70 can take, S2pro can take as well.