They have an adaptor for their regular mount lenses, at least one is shown in the brochures I've seen. Not too likely, however, that these cameras would play well with manual focus lenses. I think that for the market Nikon is targeting, lens choice or the ability to use "legacy" glass isn't too important.
I like the idea of these mirrorless cameras, but everybody else who is making one is using a larger sensor than Nikon. Supposedly, Nikon's sensors in these cams are better than the competition. I'm not in a hurry to buy one, so I'm willing to wait and see how things shake out, though someday, I'd like a digi that can do Raw, with a decent sized sensor.
But my local shop has them, and one of their guys seems to like it a lot (and bought one for himself). When he still did film, he used Leicas.