Sigma 19mm on NEX - Initial impressions

Hi

Considering the Sigma 19mm but struggling to see the the advantage over 'a good copy' the kit lens.

Physically the 19mm is a bit smaller but at f2.8 it is only half a stop better than the kit lens at f3.5 wide open and the kit lens has ois. I appreciate ois it is only good for static subjects.

Has anyone got both lenses and can qualify the differences or preferences for the 19mm?

Kind regards
Glen