I'm having a record day on Kobo. I only keep about half my catalog there because I got suckered back into Select, but it is going to beat BN like a borrowed mule.
Unfortunately, you have to "direct market" at the moment, meaning driving your own traffic for the most part. Also seeing accelerating foreign-language sales there. But they are making improvements faster than anyone, including Amazon. You just can't always see it because it is behind the scenes.
Lastly, I would ask "Why would you not be in ANY market?" Especially one where you can direct upload, change data easily, and even remove it with a few clicks if you need to. You do not know which sale will change a life (yours or the reader's.)
P.S. I run a Facebook promo wall that is cooperative, not a money maker--you share the current posted book, then your book gets posted. Details are in the note at
http://www.facebook.com/kobobooks. Give it a try!