Well it is a musical. The stage production is 3 hours sung-through, so 2.5 hours is actually pretty good.
I'd be annoyed if it did have dialogue, it doesn't need to be 'thrown in for good measure'!
I can understand people banging on about Anne Hathaway as it sounds like she is the standout, but lots of reviews have had good things to say about Sam, Aaron Tveit and Eddie Redmayne as well.
As for the amount of screentime Eponine gets:
I'm hoping Anne, Sam and Eddie live up to expectations as they have my 3 favourite solos in the musical. I'm more worried about whether Hugh Jackman does a good Bring Him Home though, some reviews I've read didn't rate it at all...
Yeah I have the soundtrack and was a bit miffed that Eponine's solo 'On my Own' had the intro cut, however if you wasn't a 'Les Mis' fan or didn't know the song(s) so much, you wouldn't have known. On the soundtrack it goes straight into 'One Day More' too.
I'm guessing that Anne's 'I Dreamed A Dream' works much better on screen because on the soundtrack it's not really one you can enjoy as much as the others because she's crying (as they are direct rips from the movie).