I've flown on a couple of the old 753s recently. Was able to book an exit row on one flight, so it wasn't too bad in Y. I got upgraded on the other flight (LAX-IAD redeye) and was pleased that it seemed to be more comfortable than the old UA 757s due to the absence of the "box" underneath the seats in front of me.
Have a couple of 753 flights coming up (SFO-OGG and return) - I'm sure not looking forward to those in Y but for $300 RT ai I shouldn't complain.