Unless your goal is wildlife, I can heartily second the Sony RX100 for UL backpacking photographers looking to replace a DSLR with something lighter and more compact.
I brought one with on a recent trip to Olympic NP (North Fork Quinault River Trail to Low Divide, looping back via the Skyline Trail) and come back thoroughly impressed.
The image quality to size/weight ratio of the RX100 is very high, and the camera has just about every useful feature and control you could want, including a well-implemented manual focusing option. Auto-focus is fast, shutter lag is minimal, the camera doesn't leave you waiting very often, and you can customize controls for quick access to useful options such as AF mode, HDR, exposure compensation, flash mode, etc. Other than the lack of a filter mount (third party options are coming), I didn't miss my 7D at all. My only request for improvement to the operation of the camera would be an option to set a minimum shutter speed in aperture priority mode or the option to use auto-ISO in manual mode.
I'd rate base ISO image quality at about 85-90% as clean compared to what my 7D delivers at base ISO, but the RX100 RAW files seem to capture a wider dynamic range. At wide angle, the lens is pretty impressive stopped down, very sharp in the center, with good (but not great) corner performance, the few detractors being a bit of CA in the corners and the lens is somewhat susceptible to flare and suffers from loss of contrast when subject to harsh near-out-of-frame light sources (a lens hood would help, but it's generally easy enough to shade the lens with your hand/hat). Battery life was great - I took about 400 photos and still had 2 of 4 bars remaining on the battery when I got off trail.
The camera also fits perfectly in a Pelican 1010 case, which despite being somewhat bulkier than the bare camera, does a great job protecting it from bumps and water/dust/humidity.