Still, I think that there is no reason to sacrifice compatibility. The differences in what is possible without sacrificing it and what is possible while doing so are IMO negligible.
EDIT: Actually, the only meaningfull difference there is that you insist that 3rd non-option parameter is "output", while backward compatibility requires "build method" (which you want to supply with -b only). Is that really worth it?
Mirek
"Should we upgrade umk command line behavior" => "Should we sacrifice backward compatibility in umk to make command line nicer?"
It's clearly a more oriented question. Only early adopters who adapt easily to new things will say "yes, we should".
Well, I think that the fact it actually IS breaking the compatibility should be clearly stated there. Which it was not.