Kobo is certainly a significant player ... in Canada ... and believably the market leader. Kindle is available at somewhat inflated prices at one chain -- The Source -- but most sales are from amazon.com. Kobo, on the other hand, is widely available, including at Walmart. Only Kobo, not Kindle, makes public library books available (in Canada). Nor has Kindle Fire been sold in Canada whereas the Kobo Vox -- although modest numbers -- has the ereader tablet space to itself.
Kobo is being sold in a number of markets outside of Canada and the US and continues to gain followers, currently claiming about 7 million active customers. It's an evolving market ... who knows where things will stand in six more months?*
*Perhaps even Pottermore will have launched by then!