I just finished my reading of The Well of Ascension not all that long ago and even though I've sent Brandon an email letting him know of how well I thought of his book I thought I'd post my opinion on here as well.
While I enjoyed the first mistborn novel slightly more (due, I think, to the incredible growth we the readers saw Vin go through) I don't think Brandon could have ever written a more fitting and thrilling second installment. The twists and turns are, in my mind, enough to boggle the mind without causing it to explode. Just when you think you know what's going to happen, WHAM, Brandon thinks it's funny to blindside you!
One thing I also enjoyed about the book was the characters. For some reason, although I loved the characters in book 1, I found myself more attached to the characters here (even though most of them were just reprising roles from the previous novel). I don't know why, but I guess it must be because the tension and danger was much more palpable throughout the book and hence helped me to attach to the characters all the more.
And I especially liked reading about two characters in particular: Them being Tensoon and Zane, although each for entirely different reasons. I liked reading about Tensoon just because he was such an incredible character and I love the nature of the kandra, and of course the plot twist at the end made me love him all the more. And Zane, well.......Zane I liked reading about because I hated him so completely. I think I must have shouted at my copy at least 5 times and pounded my head with the palm of my hand endlessly when I saw Vin trusting him and thinking of leaving with him. Yep, he was so slimy and detestable (in my opinion) that I was almost sweating everytime he had a scene with Vin.
I especially liked the ending although I remember vaguely thinking: Good God, can't you give her a break?
So all in all, Well Done BRANDON! And Congratulations on crafting another superb novel! Keep them(and the plot twists) coming!
P.S. I do want to warn all posters here though, that I think our own Brandon is an allomancer. I could have sworn he was pushing and pulling my emotions throughout the tensest parts of the story. I think we can trust him, but still, I would caution us all to be wary.
Luke