It's an interesting idea Dave, but I doubt it will give much of an advantage. If going lightweight I either make do without a tripod, or use my Gorillapod SLR Zoom. I need this big one for my EOS5D, and it has the option of fitting a proper tripod head for easier composing, though there's a weight penalty.
I'd like to have a lighter option, and really like the looks of the micro 4/3 system which uses live view to do away with the mirror. I'm sure there will be more cameras to follow the Panasonic G1 in the coming year - credit crunch permitting.
I also liked the look of the Sigma DP1, but it's limited by slow write times (during which you can't take a shot) and no zoom. Have you used this camera Chris? I'd be interested in your views with regard to picture quality for editorial work, and its use in the field. I imagine it could be a pain capturing versions of an image when eg cloud shadows are moving quickly over the landscape.
General compact cameras are great for personal use. As Chris says up to A4, which lets face it is good enough for most folks. The main limiting factor though is the lack of filters. I like to use polarisers and ND grads to control the sky. It's possible that the effect of ND grads could be replicated during processing if you use Adobe Lightroom 2. I haven't upgraded from 1 yet, but will do soon. If it works I'd consider a compact for personal use. From what Cameron says maybe even for editorial use, though I'd have thought you'd be at a disadvantage here when up against a DSLR. Would you put a limit on the picture size from a compact in TGO Cameron? I assume quality wouldn't be good enough for a full page, but possibly for half. The problem with compacts is the small sensor size, and the ever higher numbers of pixels they pack onto them resulting in noisey pictures.