When I thought Chewy was blown up I almost walked out.
When Threepio made his sacrifice I was on the verge of tears.
When Leia died I couldn't have cared less at that point.
I knew Chewie wasn't dead, cause I remembered seeing the trailer of him flying in the Millenium Falcon with Lando, which hadn't happened at that point in the film (which is why trailers are annoying spoilers in themselves)
Also, I think it would have had greater dramatic impact if Threepio's memory remained wiped, seems bit of a cop out having R2 restore it (at least partially)