I have had 4 ppds so far at photos.com: 1 X $21 and 2 X $3 and 1X $1.5.
I do not know if is worth it. I have the feeling, I get less ppd at StockXpert , becuase I am opt in for subs.
I just calculated the average earnings /dl for jupiterimages and photos.com together. For me its $ 0,4.
Just for the sake of comparision:
At SS the average per download earnings is much higher with $ 0.59/dl.