My husband and I are reading a couple of books about Medjugorje and I personally believe in it. I have not seen anything wicked or out of keeping with the faith in it yet. A lot of good has come from it, people converting, being baptised, recieving confession, etc. If it is Satan's work, it sure seems to be backfiring big time! Similar things have happened before such as Fatima.
I was worried at first that it would turn into Mary worship, but the apparition apparently says when asked if we should pray to Mary or Jesus, "Pray to Jesus!" and again, "I cannot heal you, only God can, but I will pray for you", and etc.
I'm not saying you should believe it, just that I personally do. Of course if it were proven to be false it would not shake my faith in God or religion in the slightest. It would be a very clever hoax though, and I seriously doubt that will ever happen.