My opinion is opposite of the concensus -- I didn't want to have them at our wedding for the reasons everyone has already stated, other than the kid factor as we didn't have kids at our wedding. But my husband did, so I bought some when they were on sale.
We didn't get all of them back, and are still hopeful the missing ones will show up, but we loved the pictures we got from them. We included instructions asking folks to not take pictures of us since the pro photographer had that under control, and amazingly ended up with very few of these, unless other folks were in them with us. One thing we found is that our older guests at the reception didn't use them, but my brother (a groomsman) was great about going around and getting folks at different tables to start using them by snapping shots of them. So, I would definitely recommend asking the wedding party and a few members of your immediate family that will know who the relatives are to do this for you.
Several of our friends and family members took pics using their own digital cameras, and other than our parents (who were really too busy to take too many pics), only two friends have sent them to us despite numerous requests. And like you Caribear, I always send the newlyweds the pics I take at their weddings just in the off chance I capture something their photographer didn't get and they would like to have, so I have found the fact that not everyone does this (even when asked) somewhat of a bummer.