I do not recive a notification when someone in my group sends a message in the chat. I get notifications for IMs I get from personal messages just not from the groups I am in. Not sure if it is a bug and i need to reinstall or it is a feature that is not implimented. It is a hassle to have to open up skype to see if someone has said anything in the group.
Unfortunately, group chat notifications are not yet available, but is something we hope to deliver in the future.