I liked it - mostly. I thought the acting was good - I felt a little disoriented at times, trying to recall who was reading from whose diary, but that settled down in time.
I was disappointed with the ending - seems like the Hugh Jackman reveal happened too early in the movie. As soon as we saw the pile of hats (not counting the credits), it seemed like that storyline had played out, and all that was left was to see what happened to Christian Bale. That section played out well, I thought, but it felt like the Hugh Jackman storyline kept being hammered into us.
There were plenty of lines of dialogue that suddenly shifted in meaning as things were revealed - "Consider the cost of this plan" "If you trust me, trust him", which I appreciated.
Having seen "The Illusionist", I figured that the two movies would be similar, but I ended up leaving the theatre happier with that movie. I guess there was a happy ending for some of the characters in "The Prestige", but like most magic tricks, once the explanation of how the trick is done is over, it's all rather unsatisfying.
Hm, look at that. I managed to grumble about it in enough generalities that nothing's really a spoiler.