It is so funny when I read the bunch of stupid answers. First of all, if you buy a Nikon Camera, you buy a piece of Sony since until today there has not been any Nikon camera working without a Sony capture device. In simple words, the sensor that captures your shot in a Sony Camera and in a Nikon camera are exactly the same. Note that Nikon belongs to Mitsubishi.
The whole looks different in the way that Nikon puts much more value on inside camera software cheating, mainly pushing ISO rates by flattening noise. Nikon does this quiet good as long as you do not look too close on the picture. Noise reduction is indeed the better way to destroy a shot.
Sony stays with it's cameras in the physical range of what is possible. For sure they do noise flattening as well, but do not reach the skills that Nikon reaches. Now, I use both brands and others like Fuji and can tell you that I always switch noise reduction off and stay within what the capture device can do by it's own. If I do complex things, I do this on computer software and here, even the best in camera soft can not compete. Above all, on a computer soft you select how much and where you want to flatten noise.
What I do like in Sony cameras is that they are real cameras without being or becoming walk around computers that do all for you.
A camera like A700 or A900 are among the most amazing tools I know, no useless junk like live view and artificial horizons, just only what a camera needs and, all of them have anti shake included in the body.
Sony dslr's are Minolta's since Sony bought the whole factory and it just stamps it's name on them. Those that make Sony dslr's at Minolta never have seen or met those that make Sony's Point and Shoot, and, I hope they never will.
On the end, notice that for the price of one single Nikon lens, you can buy 4 to 6 excellent Minolta used glasses on E-Bay and most of them are as good and some even better then Nikon's. If your goal is to dance in the court of those that have big money to spend, stick to Nikon. Concerning quality of material and picture, both are at equal level.