I have two fr. grips but don't use them (anymore).  I found it nearly
impossible (if not merely time consuming) to lift out a frame without
pinching or "rolling" bees betweem the end bars and the hive wall.
 
Also as mentioned, you have to loosen the frame with a hive-tool anyway;
with tool in hand you are already "there" and can remove the frame without
any added motions, like transferring the hive tool to the other hand and
picking up the frame grip (whatever).
 
I have seen others use them, and when a frame is stuck, some folks will
grab the top bar with the grips and rock it back and forth trying to loosen
it.  Suddenly the frame breaks free from the hive and the frame gets yanked
out with too much force, and too fast.  Bees get knocked, rolled, and
angry.  I guess it depends on how careful you are.  But it's much easier to
judge the force needed to free and gently remove a frame when you are
lifting it with your fingers.  Another thing is that once the frame is in
the grip and out of the hive, you can't grab it well to shake or transfer
it, because you only have one free hand!
 
I used to use the frame grip to get the first, outermost frame out.  That
was when I had 10 frames/brood chamber.  Now that I've switched to 9 I
sometimes don't even need a hive tool to remove brood frames.  Or, at least
the first frame comes out much more readily.  FWIW