Our 3yo wears pull-ups at night. She's been potty trained for about a year. Funny thing is that for the first week or two after she moved from her crib and to her full-size bed (last spring), she would cry and we would get her up to go potty during the night. However, that ended quickly and now she sleeps through the urge.
We've tried panties on occasion, but she just wets the bed. We don't mind the extra work, but it TRULY upsets her. It wakes her up from a dead sleep, soaks her and she bawls because she feels horrible that she had an accident. It's just not worth it (even though some nights it's a fight to get her to put a pull-up on). Plus, we have to clean her up and redress her which totally wakes her up and ruins her night of sleep.
I've done a bunch of research online and talked to her doctor, and basically some kids can't stay dry (or wake up to pee) until they are 6 years old. It's still within the norm (after 6 you need to see what might be going on physically or mentally). So I figure we have time. We tell our daughter that once she starts keeping her pull-up dry all night, then she can start wearing panties to bed.
Personally, I would recommend some kind of training pants at night (whether cloth or disposable) until they can make it through the night consistently. It might happen quickly or not for each child. Everyone is different. Good luck! :-)