Sigma 28-70 F2.8 EX

Hello.
Someone here knows this lens Sigma 28-70 F2.8 EX?
I wanted to know your opinion about this because I have a view in buying power.
I have a Tamron 17-50mm f2, 8, did not like her very much, because the compensation in Tamron is very different from other lenses do not know why sometimes I have to use the bracketing at -2 or -3, does not understand why, in K-10 did not need much, so this is now.
I hope your comment.
Best wishes

I'd suspect that you'd find the Sigma EX 24mm-70mm or 24-60mmm zooms a bit more useful as a range.

I used a 24-135mm as my main lens for a while and 24mm was often wide enough where 28 wasn't (from the 28-70mm I was using prior).

Can't really comment on how the lenses perform as I've never owned one of them (although often thought about it) but the reputation for these is generally good.

Were there some compatibility issues with that lens on Pentax DSLRs? It would not auto focus or stop down on the early versions before Sigma upgraded the lens.