I for one have seen Liquidsn perform his Push off in various settings, and I remember first seeing it and being astounded at the simplicity and smoothness of it.
I totally agree with Morgician on the fact that a DL that requires a break, whether it be a pinky break, thumb break (to each his own), is a sure fire way to ensure 100% accuracy, at the risk of adding a little extra tension to the hand, but that if it is done correctly, can be seemingly natural and without risk.
However, to back up Liquidsn, I completely understand and agree where he is coming from when he says, the easiest, and most natural way to push off a single, should be the EXACT same way you do a DL. Now, in the beginning of his lesson video, you will notice him doing the push off DL a few times, and then switching to a single. I at first did not even notice it, until I saw a different card... I was confused. I didnt know if he was doing singles and then finally did a DL, or if he did his push off DL and finally show a single... haha.
(sorry I was a bit tired).
One thing that I can add that hasn't been mentioned: Since the push off DL is indeed a knack, and even if practiced for a year, can still only be 99%, when you do hit that 1 % and have an un-squared double, you don't have to turn it over. You can always resquare, continue on with your patter, misdirect, and do it again. This, if you have indeed practiced, can be detected without even looking at your hands. you will know when the DL isnt perfectly squared =).
This is of course, only, if you take Liquid's sound advice, and put in the required practice time.
Lets all keep working hard together at keeping our passion for, practice, and performance of slight-of-hand at a high and respected level!