Overall, I think the officials have been bad, w/Boston game 4 being the bottom of the barrel, but they have generally been more of a D than an F.
It's long been a problem in the NBA that when there's a block/charge decision the call almost always goes to the home team unless it's really obvious. I thought the charge calls on Lebron were weak late in game 4, but those are going against Cleveland 95% of the time on the road.
At times, the officials are doing a half-decent job of no-calls on plays where the offensive guy absurdly forces the contact. In the Memphis/GS game last night there were a few instances where the other team 'got themselves a bird' and the offensive player awkwardly tried to jump into the defensive player and put up an implausible shot, and the refs didn't call it. Very good.
It's interesting that in these playoffs we haven't seen a lot of games where half the team is in foul trouble with ticky-tack fouls, such as we often see in the NCAA tourney, Instead the worst-officiated NBA games have been 90s-style wrestling matches like Game 4 in Boston, which is awful to watch and just as bad as the kind of ticky-tack stuff that has marred the NCAA tournament.