It does seem an odd choice since it essentially reproduces an existing Sony lens. It would have been nicer to see something that filled a gap like a 35/1.8 or even an affordable 24/2. I hope those will come from Sigma eventually. It would be nice if they could come up with a road map.
Probably not. I'd like something around that focal length myself; I'd also be using it for portraiture. I'd be interested in seeing output from such a lens in various contexts, up close work, portraits, short telephoto general purpose, opened up and stopped down.
Am also keeping my eye open locally for a legacy macro > 50mm for that purpose.