I probably should update this article and say that I've been shooting with the NEX 7 for over a year now. The Tri Navi controls, Magnesium body and the Fantastic EVF won me over. In the end, I really like the extra pixels and all the extra control. The additional noise turned out to be a non-issue.
If you are considering one of these cameras, you ought to read this review posted on PhotoClubAlpha. It is a great and somewhat surprising look at the issues of the larger megapixel count and all the peripheral equipment available (or not) for both.
When I have been editing NEX-7 images at their native 24 megapixels the NEX-5n upscaled image has sometimes looked better overall, and the native size NEX-5n image nearly always wins. The NEX-7 image misses the mark for me maybe 30% of the time.
I really do love the 5N and here is my review from a couple months back.
Quick Note: If you are looking for more information about custom controls, Lenses and tips for the Sony NEX series, take a look here for my guides, reviews and links.