I'd been looking for a small backup camera for my D700 kit and narrowed the choices down to the Sony NEX6 and the Fujifilm X20. Not wanting to start another system and opting for both lower weight and lower cost, I bought the X20. I am very impressed with its performance as are two Nikon DSLR owner friends.
I find that the X20's JPEG output is more than satisfactory for on screen viewing. My practice is to have photos taken with the D700 printed at 8x12" by Mpix for display under controlled conditions but I didn't buy the X20 for that purpose. However, a couple of full screen desktop photos taken with the X20 indicate to me that printed enlargements of modest dimensions would look quite good.
I've set one of the Custom positions on the mode dial to JPEG/Fine/4:3/Auto-ISO/DR-auto and the other to Raw/4:3/ISO-100/DR-off. Adobe ACR handles the X20's raw output but, as noted, I'm primarily using the JPEG capture mode.
Much has been written about the X20. Nicely made, good lens, reasonable menus, etc. The too-short battery life is well documented but batteries are cheap and easy to carry. I must, however, say that the manual is lacking. I've been looking for a third-party user's guide but haven't found one and am reluctant to buy the one X10 guide on the market as the X20 sensor is substantially different, making much of an X10 book irrelevant.
I've overcome the other minor complaint - the push-on lens cap. A pinch together 40.5mm lens cap fits nicely in the non-standard lens threads. I did remove material from the moving parts on the back of the lens cap with a Dremel tool to prevent contact with the front lens element.
With my aftermarket filter adapter/lens hood, a 52mm Nikon-style pinch together lens cap fits into the adapter ring threads. Alternatively, a 58mm pinch together cap will fit into the end of the lens hood.
I force myself to carry the X20 on neighborhood walks, something I'd never do with the D700, and have a couple dozen nice fall color photos as my reward. In all, the Fujifilm X20 is a winner.