I think they picked Edward PERFECTLY; ah I couldn't imagine anyone better. He really does suit it.
Bella is alright, I think Kristen could pull it off. Esme is good, same with the whole Cullen family actually. I just really don't like Jacob, the guy is Taylor Lautner and was born in 1992.. He was in that stupid kid movie, 'The Adventures of Sharkboy and Lavagirl 3-D'.
Here is a picture of him from then:

And here's him now:

Hmmm, I dunno. After looking at that last picture, I think maybe he could pull it off

Just have to ignore the fact that he is so young. I guess we can't judge him until we see how he is like in the movie.
I think the people that were an idea for 'Twilight' was Emily Browning and Henry something or rather..?? I think the choices are better suited now actually to be honest.
Just found a video that some girls took of Taylor (Jacob Black) acting a scene for Twilight if you would like to have a look:
http://www.twilightlexiconblog.com/?p=879