Recently switched from a Kindle to a Kobo and here are my findings so far:

Kobo Pros:

* Natively handle .epub files

* Overdrive integration for library books

* Dropbox integration so it's quick to transfer files from my laptop

* Pocket integration. Being able to read long form web articles on an e-ink screen is a game changer for me.

* OS is generally better

* Minor, but I like seeing the book I'm reading on the sleep screen

Kobo cons:

* Buttons are slightly worse than the Kindle's

* For the Sage, the battery life is worse than the Kindle. I've heard the other models are better though.