One of my friends always described RUSH as "really good at bad music," and I always thought that was fairly apt. For my tastes anyway.
Anyway, I've known about Anika for a long time, though I was surprised to see her tapped for Rush. But after I thought about it, I thought "Oh, of course, that does make some sense." She's not a "powerful" player like Peart was, but she's extremely technical and excels at the brain-bendy stuff that Peart consistently kick Rush's music in the ass with. In those regards, she's a great replacement for him.
I reckon a lot of people would've liked to see Tool's Danny Carey or Dream Theater's Mike Portnoy do a stint with Rush....they would've been the obvious choices, if they were available. But I've seen a lot of clips of Anika with them already, and she fits well, I think.