[bjornzzz]

I got it for AUD $460 shipped. Pretty good price I reckon. Yet to receive it so can't comment on condition, but if it is as the seller puts it, it should be perfect..

[simico]

I've had the Tamron 17-50/2.8 and now have Pentax 17-70/4.

I'm now considering to do the opposite: replace my DA 17-70 with Tamron 17-50

I also have the same dilemma and would also want to upgrade.

I had the same dilemma last year. The longer tele end of 17-70 was very nice and useful for portraits, on the other hand f/2.8 of the Tamron was also very desired. After a lot of contemplation I bought 17-70 because at that time the longer range seemed to be more important. Now I have the dilemma of replacing 17-70 with 17-50, because now one stop advantage and faster (and reliable) focusing seems more important to me than the extra 20mm at the tele end I borrowed and tried a fellow pentaxian's 17-50 for a long weekend and found it to be a fine lens.

Now with the new bodies having amazing high ISO capability, this one stop advantage doesn't matter as much as before and f/4 can be sufficient in low light. I haven't noticed too much difference in bokeh or subject isolation between the two lens in the 17-50 range when used indoors (smaller rooms), but of course this depends on the shooting circumstances (subject and background distances, etc).

In my experience pros of the Tamron:
- one stop faster (may not matter that much, see previous section)
- faster focusing
- cheaper (at least here)
- may come with longer warranty, depending on location of purchase

Pros of DA 17-70
- longer range, 70mm end is good for portraits
- silent SDM focusing
- very good IQ even wide open (took 95% of my photos wide open with it)

The best would be a good DA 17-70 f/2.8, I guess If you want best of both and don't mind losing the wide end (i.e. you already have a wide angle lens or you don't need wide angle) then Tamron 28-75 is the way to go