On her machine, it started out with an inability to use the trackpad when she wanted to click and then drag, that action didn't work at all. She shrugged it off, mainly b/c she needs the machine daily. Then things got worse and the pad became erractic to the point that she couldn't use it anymore. It would start by working, then halfway it just froze up, only to work again a couple of minutes later. Occasionally she had a couple of hours without problems. She brought it in, the guys checked it out and said that they needed to replace the top case (presumably they can't change just the pad but that's just speculation on my part). Anyway, they called her when the part was in, she dropped off her machine in the morning and picked it up again in the afternoon, everything ok again.
Good luck!