"Job was "perfect" in that sense because he never blamed God for his misfortunes. And God knew it."
There are parts where Job turns into a whiner and a blamer, he takes a pretty strong shot at God in 30:20-22
20 "I cry out to you, O God, but you do not answer;
I stand up, but you merely look at me.
21 You turn on me ruthlessly;
with the might of your hand you attack me.
22 You snatch me up and drive me before the wind;
you toss me about in the storm.
And God is very clear in hearing Job as the whiner that he is and slaps him pretty hard in 40.
1 The LORD said to Job:
2 "Will the one who contends with the Almighty correct him?
Let him who accuses God answer him!"
3 Then Job answered the LORD :
4 "I am unworthy—how can I reply to you?
I put my hand over my mouth.
5 I spoke once, but I have no answer—
twice, but I will say no more."
6 Then the LORD spoke to Job out of the storm:
7 "Brace yourself like a man;
I will question you,
and you shall answer me.
8 "Would you discredit my justice?
Would you condemn me to justify yourself?
True, but he never gives in to the devil. We have all experienced "low" moments in our faith, and have often felt that the Spirit has "forsaken" us. Even Christ, in His human nature, repeats that on the Cross, about God abandoning Him. Does that mean that Jesus sinned?
When He asked the Father if it would be possible to pass the cup that was awaiting Jesus, was He losing faith and trust?
No! He is showing us that in adversity it is much more difficult for a human being to persevere then when things are going hunky-dory. It's easy to bless God and thank Him for His gifts; but how do we react when things begin to go haywire? Do not so many Christians protest "I am a Christian, I go to church every Sunday, I do charity; how could God allow this to happen to me?" You bet!
The bottom line is that Job wavered, as would be expected, but never crossed the threshold.