Well, having been raised a Roman Catholic with a Lutheran mother and a charismatic aunt. 
Wow.
Are we talking doctrinally, or practically? Or both?
I will go with both.
1.  I did get born again/saved while a Roman Catholic.
Ie, they teach that Jesus is lord and that God raised him from the dead.
See Romans 10:9-10
2. One nun taught me that God is the supreme being and that God is perfect and that everything that He does is perfect therefore God's word is perfect.
I was excited about that and wanted to hear more, but she stopped there.
3.  This same nun read the record of the day of Pentecost to us.  She said the pope was trying to decide if he should sanction speaking in tongues or not.  The nun said that there are charismatic catholics who speak in tongues.  I decided that the pope was not qualified.  It is so clear that the apostles spoke in tongues.  I decided that I wanted to speak in tongues.
I concluded that,"if it is good enough for the apostles, it is good enough for me"
4.  That nun read to us what the great mystery that Paul wrote of is.
Ephesians 3:6   
5.  They taught the ten commandments but they taught it as if we are under the law for righteousness.  We are not.
Salvation and righteousness are gifts, gifts are not earned, wages are.
6.  If I have my facts straight, I believe that it was the nun who taught the origin of the Devil and devil spirits from Ezekiel, etc.
I cannot think of any thing off hand that they got right.
wrong?
Other people have done a good job of listing those.
oatmeal