netmeg - 1:31 pm on Mar 20, 2013 (gmt 0)
I don't have responsive ecommerce sites as yet. On my information sites though, my mobile users are probably more than half the traffic now, with millions and millions of pageviews. The first thing I noticed is that time on site and number of pages per visit for mobile went way up. I definitely think the usability improved - not just because I try to fit most screens now, but also it caused me to trim some of the excess for desktop, so that it wouldn't get in the way of mobile.
I have at least one long form on the site (for event submission) and I never thought anyone would fill it out via mobile, but darned if they don't. So I looked into how I could shorten that up some.
But I don't know that I could say it was an SEO improvement; the sites were doing pretty well to begin with.