I've sat here reading reviews and comparing prices for a long time, and I'd more or less decided on the Pentax 50-135.
Then I checked the latest UK prices and there isn't that great a difference between them now, and I've had a little windfall so buying the cheapest isn't a deciding factor.
So now the Tamron is looking like the favorite, but I like the stellar reputation of the Pentax. I've had a long history of using Tamron and like them, but I want the weatherproofing of the Pentax.
A guy I know has the Sigma, it's a great lens. Still tempting.
And what about a used Tokina?
I'm still confused..................