At what stakes can you be certain your opp. are using Poker Tracker?

I was pondering this earlier today and I was clueless as to what stakes I could assume the majority of my opponenet were using PT. I started at the .5/.10 but I think I am in the minority of overall users. I am sure though as you go up maybe to .50/1 however you will find alot of it?

HELP~

[AcesUp2121]

I play $200 6 max and I don't use it, I imagine it's pretty popular there though.

[Isura]

A lot of very good players at the high stakes don't even use it. Among 2+2ers it's very popular, but 2+2ers make up a small percentage of online poker players.