I hope this helps some others like me who want to convert a whole bunch of files from RAW to some other format.
Darktable will then export the files in TIFF (or whatever) format. The images themselves are sitting on an OCZ Vertex 2 which can feed some 200MB/s+ - if secondary storage was the limiting factor then it would convert all hundred or so images in under two seconds. Click the EXPORT button in 'Storage Options' - see Step 1 above.Alternatively, use the SELECT ALL option near the top-right of lightable UI.Sadly, you can't see this very well on the screenshot, but I hope the reader understands the strategy.
Use CTRL and LMB to multiple-select RAW images. Set the desired path for file export to disk, and conflict options. The process can be adapted for your own conversion requirements, but I wanted 8-bit TIFF - the reason why is irrelevant. (Other command line converters can be used instead. After some exploration, it is actually quite straight-forward. RawTherapee command line interface rawtherapee-cli converts NEF file to a temporary PNG file -n with 16 bits per channel colour depth -b16 (which is good for future retrieval details from shadows etc).
