I have mixed feelings. I hate it when it's crowded, because that's when the ugliness (i.e. pushing and shoving, ignoring children, elderly, and handicapped people) comes out. I'm big enough that I'm kind of hard to push around. I don't get violent, I just don't move when pushed, and don't allow anyone to put a hand on me (I just remove the hand that is pushing me, with a smile).
I'll admit to having once performed a bit of a rugby tackle on one squirt who shoved my girlfriend. He waited until I he was off the train, then told me I was a ben dan. I sort of agreed with him, and the comment was really hilarious, so I just laughed.
I also find the MRT really convenient, and a great way to save money on transport. So it is worth the hassle most of the time.
I use the EZ card.