I thought I read that the Pentax (and Sony) version won't have the OS since they have in body. Also since this isn't an EX lens I don't know if it will be up to the same IQ as the Bigma. When I 1st saw it I thought it was a Bimga replacement but someone pointed out that it replacement for the 170-500.
But who knows, the 17-70 isn't an EX lens and is great, so maybe we'll all be happily surprised
