The ending was actually very good, just as I'd hoped. The idea that Topher sacrificed himself for undoing all the wrongs which were mostly his fault was perfect. His character had grown the most. And its not a surprise coz Joss Whedon is a genius in long term developments of characters. Best part of the Epitaph Two for me was when Echo cried and screamed at Sierra acknowledging Paul's death... I cant remember Eliza Dushku ever playing such part, she was amazing at it, it was very nice to see her that way and not as a tough cool girl for once. I liked how Adelle turned out eventually too, she became like a mother of some sort to all of them.
One thing I didn't quite get is this: did Echo imprint herself with both her and Paul? Can somebody please clear that up for me? and your thoughts on the ending too)
PS: Joss Whedon had proved once again that he's a genius at everything he does.