iframe does not pass PR. So when it comes to iframes PR does not effect its value. Its all about traffic.
pr is only related with the backlinks. if there is a page which is giving link to your ifrane page, it can have page rank but in generally iframes does not get page rank
Right click on the iframe page, copy the url and paste into browser to find out. Iframe does pass PR - seen this and had this too .
I think SEs are smarter these days even with Iframes. I would be suspicios about PR pass from such pages a year ago, but now I think it is ok for passing PR to your page..
We can all make educated guesses but knowing is the must. My last experiment did not show iframes passing PR. vicdigi What kind of experiment have you done then?