I really, really like it as a diminutive of Mairead. It's sweet, happy-sounding, and as you said, charming. I would refrain from using it as a full first name, however. Those -ie names do sound youthful and cutesy, so I would provide a full name in case one would want to switch over as they grow up.
I did cull it off of my PNL when I went through it a few weeks ago, so I suppose I don't like it quite as much as I used to (though I did cut down on over half my list).