Thanks for the helpful replies. Using 240ppi will obviously make a difference for upsizing files.
I'm still not convinced that what I'm coming up against aren't the resolution and dynamic range limitations of the camera (chip, processing, etc.) But I'm hoping to find that I'm wrong! I've certainly got a lot to learn about digital image processing.
Most of my shooting is of people going about their business indoors in mixed lighting, usually from the dark side, and often with bright window highlights behind. I use incident readings from the dark side for that situation - which usually means that I'm giving several stops more exposure than the R-D1 would if set to automatic.
I have shot colour negative and the R-D1 together in the same situations, at the same speeds (400 or 800) and with identical exposures (often 125th or 60th at F2). I don't have any problems getting good shadow detail and tonality from my film/digital workflow, using a Minolta 5400 scanner, PS CS and Epson 1280 at up to 14x11.
But I do find that the R-D1 prints, which look ok at first glance, often have ugly transitions into the shadows on the fleshtones. Where this is noticeable is as the light falls away across a cheek, or where hair casts a shadow on a face - or in the modelling from light to shade across an arm. With film I have fewer problems getting gentle transitions that read across the flesh contours. But with the R-D1 I'm finding it much harder to get the same results when shooting in the same way. Detail and range of tonality in dark or shadowed hair are also a problem.
I usually don't pick up the problems on screen - it's only on the prints that its obvious.
I don't think I'm underexposing the R-D1 files. The histograms look ok, without obvious clipping (except in highlights that I don't care about). I obviously need to work harder at extending the range of shadow tonality in post-processing.
At this stage of my experience with the R-D1 it feels that for the kind of documentary-style shooting I do most of the time, with variable and poor interior lighting, often of the shadow side, I'm finding the same kinds of limitation that I'd expect if I was shooting with fast slide film - compounded by some resolution limitations.
I hope I can start to prove myself wrong....
Simon.