Whether you're mad or not depends on your own usage.
All I can tell you is that I pre-ordered the NEX7 so I could use my Contax G2 Zeiss lenses more than anything else, and eagerly anticipating the release I got the converter to fit the Zeiss lenses, a card reader and a couple of cards only to be faced with this indeterminate delay, so I went and got the 5n intending to pass it on when the NEX7 finally comes, but the missus has taken a real shine to it so I'll have to see how that one pans out.
All I can tell you so far is I'm completely blown away by the 5n in pretty much every respect, image quality, noise performance in such a small package is just not heard of previously. It's easily the equal and probably better than a lot of current DSLRs . I'd unhesitatingly recommend it.
The only thing I'd say is that the NEX lenses are OK but not brilliant, and while there are a couple of Zeiss options available for it the range of Sony lenses so far isn't great, although there'll no doubt be more to come.
I won't be dropping my DSLRs for bird photography with long lenses, but for general purpose, walk around, street and landscape stuff- even portraits I can see it getting a lot of use.