I have no problem with it. I have it on a couple of classes, and I'll switch to them if the other team calls in a blackbird.
The only thing I don't like about the Ghost perk is the ghillie suit, Russian marshmallow suit and the Spanish Ragbag.
They are stupid outfits and should be removed, they are so OP.
I personally don't have a problem with it but I think it has to do with the fact that the spy plane is used so often that people tend to rely on it. Kill streaks don't add to the next making spy plane a common one so you know where every one is and when some ones kill streak reward is rendered useless they cry about it.