Someone asked me which camera they should buy, the Sony NEX-7 or the Nikon D800?
The two cameras are much different. The Sony NEX-7 is a pocket camera that has 24 megapixels on an APS-C sized sensor. The D800 is a DSLR camera that has 36 megapixels on a full-frame sensor. The Sony NEX-7 retails for $1,350 with a lens, while the Nikon D800 retails for $3,000 for the body only.
Both cameras have more resolution than 99.5% of photographers need, but the D800 does have more resolution than the NEX-7. Both cameras produce quality, sharp images and can be used to craft great photographs (as all cameras can).
The NEX-7 cost significantly less and that might be a reason to choose it. After purchasing a lens for the D800, your grand total could be over $4,000 (depending on the lens you buy). That's three times more than the cost of the NEX-7, and the D800 is not three times better of a camera.
If money is not an issue, the D800 is the better camera. Aside from medium-format, which will cost at least ten grand, the D800 is the best digital camera one can buy. If you simply want to buy the best camera you can, the D800 is that choice.
But buying this camera won't make you a better photographer.
If you already have a Nikon system, you might want to stick with a Nikon DSLR so you can use the lenses you already have. That's certainly a legitimate reason to choose the D800.
If you are a portrait or wedding photographer, your clients will make judgements on how good of a photographer you are based on the equipment you have. This judgement is based on false assumptions, but it is still there. The D800 would be the better choice for you (even though the NEX-7 would be just fine for portraits and weddings).
The NEX-7 is more fun. Any camera that fits in your pocket is a blast compared to a bulky DSLR system. If you were to purchase both cameras, you would find yourself grabbing the NEX-7 for everything except work that someone is paying you for (and even then you might still grab the NEX-7).
Finally, if you are (or would like to be) a street photographer, you'd stand out with a D800 in front of your face. You'd blend in a little better with the NEX-7, and that could be the difference in getting "the shot" or not.
The Sony NEX-7 and the Nikon D800 are both great cameras and great choices--you can't go wrong with either. Whichever camera you decide you won't be disappointed with. My advice is to not worry so much about it. Whichever one draws at you a little more, choose that camera.