I did it on the tube twice a week when I took DS to his CMs. Lifts are rare.
Omce a woman in front of me got her buggy slightly stuck on the escalator. She panicked, I leaned over and lifted her buggy off the escalator. Had I not been there it could have been pretty unpleasant.
I was aware before then that it was potentially quite dangerous, but after that I was especially careful to keep my wits about me and make sure I paid close attention to what I was doing.
The alternative (holding on to my uncooperative, prone to running off, young toddler while folding the buggy, then carrying all my bags, child and buggy up an escalator at rush hour) didn't seem like much of one.
The other alternative (don't take the tube) would have turned a 40 minute journey into an hour and a half bus journey to take DS to the CMs before work.
Having said that it probably is really unsafe.
I've gone for a different solution now, I've moved out of London 