I've got/had a couple of Sigmas and been perfectly happy with them. But, one thing to consider that swung me to the DA 12-24 instead of the 10-20 was that the supply of new K-mount stuff generally is currently tight. So if I did finally get one and it was dodgy there was not much chance of getting it replaced reasonably quickly. If I could reasonably expect to just be able to send/take it back and try another one, I might well have got the 10-20 instead.

(Of course it's always possible the 12-24 will be dodgy - haven't got it yet - but the odds seem better).

MostlyHarmless