I've been publishing exclusively on Amazon since the beginning; I reasoned that it was a good choice because of the learning curve involved with effectively publishing directly with Kobo and iBooks. I also reasoned that being exclusive means I could continue to participate in Kindle Unlimited and other promos like the Kindle Lending Library.
This week, both books in The Olivia Chronicles are live on Smashwords (for those of you who read on a Nook, this is a good spot to get my books). I also published on Kobo and on iBooks (book 2 has yet to go live, but is in the QA process), as well.
The learning curve is not that bad; once you learn how to shift the TOC from your print versions to bookmark anchored TOC, the files clean up pretty quickly. You will, if you don't have a Mac, need to use a third party like Draft2Digital to publish on iBooks.
I'm working toward the end of Book 3 (as yet untitled) and will be publishing in all platforms from the start with that book. I'm open to giving coupon codes (this is something that I couldn't do before with Kindle only) for review copies of Book 1 and 2 if folks email me for those codes.