Nick,
I think Demetra is ‘better’ than ISIS in terms of a more intuitive software. I was also a Demetra beta tester and the software was designed by Francois Cochard and Nicolas Durand to make the accurate processing of Alpy spectra as straightforward and reliable as possible and in that I think they brilliantly succeeded. BASS is a very intuitive software as well which I have used extensively for my data reduction. Both Demetra and BASS will help ensure that the complexity of data reduction is as low a barrier as possible to getting more people practicing amateur spectroscopy. That for me is their key attraction, whilst ISIS will remain the ‘gold standard’ in terms of, as Robin said, its flexibility and comprehensive performance
Cheers
Hugh