It is still on my dream list... I do have a F2.8 constant ap tamron 28-75 that I have used for some club shots...
If you are asking about festival or big concert shots with a full-on mega-watt light shows then the 2.8 will work fine. (how do you get that camera and lens in? Press Pass?)
But for club shots where it is pretty low light by comparison then 2.8 really pushes you into the ISO 1600 and 3200 range. And I am not sure the K10 is the right sensor for that.
Here is a iso 3200 jpeg from the K100d w/tamron 28-75 at 2.8... it printed out nice, although I will not be making any posters from it
I should add this is flashless... obviously if you are close enough to use flash the F2.8 is not even needed
Cant wait to see what the DA*50-135 gang has to show us with the concert shots... there must be a bunch out there.