To begin with, there was zero development in the supporting characters. They all seemed flat, written in the same voice, and a carbon of each other. I had trouble even distinguishing the crew members (for example Ham and Clubs). There were a lot of old-school fantasy cliches, easy to predict and without offering any surprise (spoilers: The Kendra being none of the crew members, Vin eventually choosing Elend and fighting/killing Zane & Straff while sparing Cett, etc). Finally, more than 100 pages have been spend in boring and repetitive topics, such as how Kelsier inspired the crew members to keep fighting, how Vin loved Elend but believed she didn't deserved him (and vice versa), and so on.
“At first glance, the key and the lock it fits may seem very different," Sazed said. "Different in shape, different in function, different in design. The man who looks at them without knowledge of their true nature might think them opposites, for one is meant to open, and the other to keep closed. Yet, upon closer examination he might see that without one, the other becomes useless. The wise man then sees that both lock and key were created for the same purpose.”
All in all, if you really want to know what happens next in The Final Empire, and want to follow Vin's tale, you should read the book. But if you really loved the first book, and found it perfect as an individual story, I would suggest skipping the rest (although i'll have to finish the trilogy before offering a complete and unbiased opinion). I found only 3 positive reasons to read The Well of Ascension, first being the well described and exciting battles (though with predictable results), second being the world building (though it was simply expanded from the 1st book), and the tension (yearning to learn what happens next) being the final.