Looking at a list of the best lineups in the league this season, the guys a power forward would have to defend include:
Ibaka
Green
Aldridge
Love
Millsap
Patterson
Griffin
That's not even counting the bigger threes that could get switched onto a power forward, like Durant and LeBron.
All of those guys can stretch the floor out to the three point line.
None of them is really likely to kill you on the glass, though.
At the same time, with the exception of Patterson, all of those guys should -- at least in theory -- be able to punish smaller or weaker defenders in the post. Ibaka and Love haven't always been able to do that in practice, but I think that may be due at least partially to the fact that they aren't involved in their teams' offense enough to ever get into a scoring rhythm inside.
I think it's fair to say that fielding a guy at power forward with the natural strength and post defense of a wing can still be a significant liability against the best opponents. At the same time, I think it's clear that the likelihood of facing an opponent with a 4 that gets a significant chunk of their offense by working out of deep post-ups with their back to the basket is fairly low.