I don't need them to try for an exact match. Heck, I liked Lois in Smallville (most of the time) and she doesn't look like a traditional Lois. My problem with MoS Lois (well, the biggest one) is that she's extremely bland and not memorable. I could see myself watching the movie and then just forgetting who she is if they don't keep constantly calling her name.
I mean, in a perfect world, comic book movie actors would look like the comic book counterparts all the time. I'm watching a movie based off a franchise I like, I'm not there to see them pull out some random actress, call her "Lois" and then just have to accept that this random woman is the character I'm used to. If you're not going to use the characters normal liknesses/personalities, or close to it, why bother to use them at all? Its like casting Patton Oswalt as Thor or Christopher Walken as Captain America. No one in their right mind would do that, because its just stupid. MoS Lois isn't that bad, but she is bland and forgettable. Still, I don't need characters to be exact. I was fine with black Heimdall in Thor and stuff likie that, but you should be able to identify a major character on sight, and the actress for Lois is just too bland for that.
That said, a forgettable Lois is a very small problem in a movie that looks to be full of them. I just mentioned it because I started noticing it.