Originally Posted by Biro
If the OP decided he wanted a GX1, I hope he jumped on the one-day special at Amazon.com last Thursday.
That was the best deal on body only, but there are still good deals on the kits.
To the OP: The Nikon DSLR has slightly better sensor image quality than the GX1. When you add lenses, which you have to do if you intend to take any pictures, then the image quality depends as much on the lenses as it does on the sensors.
For portraits at usual portrait working distances, I prefer the image quality of a GX1 and Oly 45m f/1.8 to that of a Nikon D5100 and AF-S 50/1.8 or 50/1.4, and the difference in DOF control is marginal. I also prefer the GX1 and Pana 20/1.7 to the D5100 and AF-S 35/1.8. If you want more shallow DOF possibilities, sub the Pana 25/1.4 for the Pana 20/1.7. The Pana 25/1.4 is a closer match to the Nikon 35/1.8 in terms of angle of view and DOF. The former costs more, but it also produces nicer looking results to my eye.
Panasonic colors are a matter of taste. If you don't like them, you have three good options: 1) Shoot RAW and process in 3rd party converter (eg, Lightroom, Aperture); 2) Change the settings in the camera to suit your taste; 3) Postprocess the JPEGs to suit your taste. Depending on your budget, Alien Skin Exposure 3 is an awesome Photoshop/Lightroom plugin that lets you simulate the look of dozens of old film stocks. Lots of fun and easy to use.
Bottom line: The Nikon is great, and so is the GX1. I prefer the GX1, and I'm guessing you'll prefer it too. The great looks and small size will make you want to carry it, and the image quality is excellent.