I agree with the comment on Elend. Ryan Gosling is a little too pretty....and old. (I'm sorry, I'm big on age with actors and roles....I think that a 30 year old shouldn't be playing a 20 year old if there's plenty of 20 year olds available....which there are..and I know Ryan's not 30. He's only 28, but still. Close enough.)
I like nearly all the other actors chosen. Never considered Gerard Butler for Kelsier, but....wow. I can see that. He'd do a good job. Love Gerard. He rocks. I also never would've pegged Colin Firth as Dox, but that one works well too. Of course, that just might be the picture, but still.
I'm not sure about Stanley Tucci for Breeze. Age-wise, he's close to being right (I imagined Breeze around 40, and Tucci's 48), but appearance, I don't know. Tucci's bald, and Breeze, I'm pretty sure, has a head of black hair, and maybe it's starting to turn gray (I can't remember exactly). Plus, Tucci's not exactly on the 'plump' side. Breeze is....(I'm pretty sure)
The rest of the actors are pretty darn good (Marsh? Great. Skarsgard as TLR? Awesome. And I laughed at Ben Foster as Zane. Good choice), but the one I love is Spook. Oh. My. Word.....Perfect. I haven't been able to find a good Spook yet, but now my search is over....Bravo.