I tried Poker Stars quite recently and they didn’t last long on my sites. The conversions were shockingly bad so I did a couple of sign-up tests myself. None of them were credited, despite definitely qualifying for the CPA reward.
I e-mailed Poker Stars more than once asking to discuss the issue and they ignored me every time.
Bottom line is that I don’t trust ’em as far as I could throw them and I can’t promote them for that reason.