It's so-so. It depends on what tamagotchi, when you have time, if you know what it is. I think it's king of like hatching your tamas together and keeping the group info updated. If you guys need to know, just look at the pinned topics on the group hatching forums.
I think they are pretty fun! I've only participated in three before. They are only fun if other people are active, though. Otherwise it is kindof, well, boring.
(A group hatch is when a group of people either have their Tamas get married and have babies (which I do) or they reset their Tama, on the same day and occasionally at the same time. It's called a "Group Hatch" because your little Tama eggs are "hatching" along with someone else's Tama.)
Don't smack yourself! Just because you didn't do one doesn't mean you should smack yourself! I know so many people who do that. Then they just get hurt by doing it over and over.