The "denominational scoping" here is a red herring. All traditions are going to have the same view of Lukewarm Christians and non-Christians alike. It is obvious that a person who has rejected the faith or is no longer growing in it will cause disappointment. Heck, Michael W. Smith even wrote a pretty good song about it! But, what else would you expect?
I can tell you that good, well-sourced answers are going to focus on the church in Laodecia (a town I've been too, btw. If you can convince the guard to let you in, it's amazing to be able to walk around the ruins by yourself!). That verse says:
“To the angel of the church in Laodicea write:
These are the words of the Amen, the faithful and true witness, the ruler of God’s creation. 15 I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! 16 So, because you are lukewarm—neither hot nor cold—I am about to spit you out of my mouth. 17 You say, ‘I am rich; I have acquired wealth and do not need a thing.’ But you do not realize that you are wretched, pitiful, poor, blind and naked. 18 I counsel you to buy from me gold refined in the fire, so you can become rich; and white clothes to wear, so you can cover your shameful nakedness; and salve to put on your eyes, so you can see.
19 Those whom I love I rebuke and discipline. So be earnest and repent. 20 Here I am! I stand at the door and knock. If anyone hears my voice and opens the door, I will come in and eat with that person, and they with me.
From this, you are going to get the term "lukewarm Christians," pretty much regardless of the denomination.
My question for you is: What about them do you want to know?
To clarify, the terms you have brought up are different, and only the term I brought up (lukewarm Christians) is specific to Christianity.
Aposasty: This is defined as rejecting any specified faith. In Muslim countries, a person who was a Muslim but becomes convinced of the words of Jesus, for example, will called an apostate. In several Muslim countries (e.g. Pakistan, in particular) this is a crime punishable by death.
Backsliding: This is less than rejection. It is making a commitment - sometimes even a vow - and then no longer choosing to hold to it. If I were trying to give up sniffing glue, but I chose the wrong week to give up sniffing glue that would be "backsliding".
Being Lukewarm: This is an explict Christian reference (see above), but it can be true about anything. If I'm ambivalent about sports, but don't hate them, I'd just be "lukewarm" about it. When it comes to something as dramatic and life changing about one's personal relationship with the one who made him and the one who will save him, however, that ambivilance would naturally be percevied as repugnant by those who feel "truly saved".