Have to admit that it's more about Harry's line at the end of the possession than the possession itself...
I personally loved the possession scene. It really freaked me out.
The first time I watched it I froze during the whole scene. At first when he coughed and Dumby turned around looking confused it was just funny. Dan looked kinda scary, writhing in pain with shining green eyes and speaking in a voldy/harry voice. The part with the mirror was great, when he saw himself with Voldy's head saying "look at me".
I began crying when Voldy went through his memories and taunting him ("so weak, so vulnerable..."), and cried even more just before Voldy let him go and Harry lay all helpless on the floor.
I have read the books several times, but I was like "OH NO HARRY'S GONNA DIE IN THE MINISTRY!!"
And then he smashed the mirror and was released...
One thing bothered me, though.
Why did Harry say "You're the weak one - you'll never feel love or friendship, and I feel sorry for you"?
Didn't Dumby in the books say "Voldemort has never had a friend, nor do I think he has ever wanted one" (or something) and "Voldemort does not love; he only has love for himself"?
It's not like Voldy's mourning his lack of emotions - he's convinced that love makes you weak. Wouldn't he just laugh Harry in the face if he said something like that?
"We've got something Voldemort hasn't!!"
"And what's that, Harry?!"
"Something worth fighting for!!"