Is Skype messaging reliable?

I've never really been a Skype user before, but my company recently moved into a new building that has extremely poor cell reception and I decided to give it a try so I could message my wife over WiFi during the day. So far my experience has been pretty poor on Windows Phone 8.

I seem to get notifications of new messages right when they come in, but when I launch the app to read them I could be waiting as long as 5 minutes before those same messages actually appear in the conversation window. This doesn't happen every time; it seems to be pretty random whether it's going to be responsive or not.

Is this normal? My WiFi signal seems pretty strong with all other apps, it's just Skype that's giving me trouble. Has anyone else had trouble with Skype IM on Windows Phone 8?