From Adobe® Marketing Cloud, although now a bit dated (March, 2013), this survey of 3,075 users in North America in Europe had a few key takeaways:

“Prioritize tablets. As reported in the Adobe Digital Marketing Index, tablets provide engagement levels nearly equivalent to desktop and laptop computers http://success.adobe.com/en/na/programs/digital-index/1205_13926_di_report_rise_of_tablets.html)…plan and prioritize optimization efforts for tablet experiences that are unique and different from smartphones, given the larger screen size.”

• Android had nearly 2:1 market share compared to Apple iOS but iOS users re-emerged as system of choice for browsing as iOS users “tend to be more engaged” and “tend to be loyal, having both iPhones and iPads to stay connected…”
• Use of tablets as primary device doubled from 2012-201 from 12% to 23%
• #1 item requested by mobile (smartphone and tablet) users to improve their experience was to “improve ease of use” (25%)
• Mobile applications vs mobile websites were very similar in customer satisfaction when shopping for consumer products
• A significantly larger % of users are spending more than $500 annually on tablets than they are on smartphones (33-50%!!!)
• “…location-based offer, such as an in-store display…should take advantage of the ability to dynamically personalize the brand experience for their target audience.”
• “Marketers should consider providing more incentives to drive check-ins if their business has a physical location.”