Totally didn't get this movie...
This movie is essentially a re-working of Bad Santa...
Loathsome character meets screwed up kid, moves in with his family and -- in a roundabout weird way -- sorta helps the kid deal with his issues.
That said, my wife and I thought this sucked. Nothing to do with JGL who makes the best of his role... it's just that the story was confusing and lame.
For example:
Hesher moves in with this family. Except for the kid, nobody much acknowledges him or questions his presence. (Done in Bad Santa as well...) Like a lot of people I initially thought he was an imaginary character which might have been interesting... but turned out not to be.
Like Billie Bob Thornton's character, Hesher is essentially unlikable. At least BBT was periodically funny... Hesher is just an unfunny a$$h0le and a psycho.
The final funeral scene was just bizarre. "On account of my stupidity, I lost my nut and, hey, that's sorta like losing the people you love. What say we take this casket out for a spin?"
The family's redemption at the end -- like the weird funeral scene above and the crushed hunk of car in the driveway is supposed to be cathartic somehow?!
Both Natalie Portman and the kid were horribly bland... at one point, I was thinking "Hey, this conversation reminds me of Napoleon Dynamite... but not funny or interesting..."
Consider me a contrarian... this movie was a dud...