Teeny tiny spoilers for the Avengers movie if someone hasn't watched it.
So I'm not sure if anyone else has covered this yet (or I'm bad at using the search function) but among Thor fans, not to mention moviegoers, there has been considerable confusion as to what the hell is going on with Thor at parts in the movie. Namely, questions pertaining to the nature of his power, and whether he is holding back or not. Since I still have not met another person who sees it this way, and am still frustrated when I look through and listen to debates over who (in the Avengers movies) is stronger, I'm going to put forth my hypothesis on the nature of movie Thor's power and godliness.
Thor's godliness and base level of power is dependent on his armor.
This is because:
When Odin casts Thor out of Asgard, he systematically takes away parts of his armor.
Armor Circle (representing a realm not of the three highest, in my opinion) - "You are unworthy of these realms!"
Cape - "You're unworthy of your title!"
Right Arm armor - "The name of my father!"
Left Arm armor - "And his father before!"
Everything else - "I, Odin All-Father, cast you out!"
As we can see, Thor is systematically de-powered and thus turned "mortal" by the dismantlement of his armor. Mjolnir, his hammer, may have been his "power", but his "godliness", his Asgardian-ness, came from his armor. We know that Thor is still a god in terms of durability and strength in the movie universe, without his hammer. Yet, he was as weak as a mortal (albeit a pretty strong one) and just as durable. (i.e, his fight to get into the SHIELD base, his vulnerability to being hit by vehicles, his one-shot defeat from the Destroyer, the fact that a group of weak mortal doctors were able to restrain him, his vulnerability to the sedative they used) So from this example, we can hypothesize: Thor's godly attributes come from his armor. Incidentally, this also fits in with the movie canon, where the Asgardians are just extremely technologically advanced aliens. The armor is their technology that gives them strength, speed, and durability far beyond a Midgardian.
This brings me to my next point:
What people often overlook in the Avengers is Thor's conversation with Agent Coulson. Each of the Avengers has an "inner struggle" in the movie. Thor's is that he's too damn powerful for Midgard, and when he fights, he ends up causing a lot of collateral damage.
"We come here, battling like Bildschlien (sp?). They are repulsive. And they trample everything in their path."
Thor's struggle is between his necessity for power to bring Loki home, and the potential damage he could wreak on innocents. And as we can see, corroborating this, and taking 1 into account:
2.) Thor is at a GREATLY reduced power level at all points in the movie until the final battle.
Thor arrives on Midgard with no armor for his upper arms. (and I could make the case for a lighter chestplate than his in the Thor movie, but it's more debatable)
Thus, we can say that Thor arrives on Midgard at a fraction of his power. How much is up for debate, but it is a pretty solid assumption to make that he arrives in a weak state. Though, I will make these arguments:
Thor's armor for his arms: the name of Odin's father, and his father before. What makes Thor so much ridiculously stronger than other Asgardians save Odin? Odin's power, due to his bloodline. Also, how does one apply force with Mjolnir? With one's arms. These points stand on less solid ground, but I think a good case can be made for them.
So, even without taking into account that Thor purposefully holds back in his fights against Iron Man, Cap, and Hulk, his baseline power level is already weakened a considerable amount. When you take into account that he does hold back, you see that he is thus using a fraction of a fraction of his true strength and power. He is holding back through conscious will not to kill or cause collateral damage as well as holding back through the limit he put on himself through his armor.
When we see him on the Helicarrier, Thor has changed to a much simpler version of his armor than even when he first arrived on Midgard! His chestplate is a much lighter version, missing a lot of armor as well as two realm-representing circles, his bracers on his arm have dwindled to barely anything, and he has done away with his cape. All of this fits in with his internal struggle in the movie, to limit his collateral damage. It makes sense that on the Helicarrier, an enclosed space where things can get ugly real fast, that he limits himself even further.
From this, we can see that when he fights the Hulk, he is at a fraction of a fraction of a fraction of his true power. His maximum power cap is even less than it was when he first encountered Iron Man and Captain America, and he is STILL consciously holding back against Hulk, not wanting to hurt Banner and instead communicate with him: "We are not your enemies, Banner! Try to think!"
There are debates on whether Thor was truly holding back in the Avengers. While I can't say for how hard he chose to swing, this power cap put on himself through his armor certainly would conclusively answer this question. Yes.
This brings me to my final point, clearing up what happens in the meadow in the Avengers after Thor escapes the containment pod.
At this point in the movie, there is considerable confusion. Some people think he couldn't pick up the hammer because he was suddenly somehow unworthy again, some people were just confused and glossed over the scene in anticipation of the final battle. But:
3.) Thor picking up his hammer in the meadow, and regaining his armor, is both the culmination of his inner struggle, and his return to his full power potential.
Initially, as Thor stares at Mjolnir, he is still conflicted. After his encounter with the Hulk, he realizes he will need more power to fight in Midgard, as he was unable to easily overpower Hulk on the Helicarrier, and prevent Hulk from destroying a good chunk of it and putting lives at risk. However, he still struggles with his fear of doing massive amounts of collateral damage, just like the Hulk did. Now, the reasons why aren't really stated explicitly in the movie, but the choice Thor makes is clear. He needs all of his power. Perhaps rationalizing that if he doesn't go all out, much more damage could be caused by beings like Hulk, and that it might cause less damage to overpower them with all his strength.
Regardless, he picks up his hammer, and summons his armor, returning at last to his full outfit. And thus to full strength.
In short, the scene where Odin banishes Thor, the scene where Thor talks to Coulson in the Avengers, and the constantly changing state of his armor I believe provide three points of strong evidence to the nature of Thor's armor, his power, and the question of whether or not he was holding back in the Avengers, and if so, by how much.
And as a last side note: Thor still never fought in his complete armor. He has never fought with his helmet on. Would this actually strengthen his power even further, or is it simply used by the directors to make Thor's face more visible? (I honestly think it's the latter, but it doesn't mean it couldn't ALSO be the former...)