I've also seen a long-term upward adoption trend for Square in small businesses in my area. Some of these are at their first-time accepting credit cards, especially at local farmer's markets where Square's adoption has increased from a fringe payments player to near ubiquity (>90%) over the past three to four years. It's also been interesting to see an increasing trend in businesses switching to Square from traditional wired or wireless credit card systems.
Every time I hear that Square isn't doing well financially, my heart sinks a bit. From my experience, it seems that they're nailing an underserved market and greatly improving the experience for these small businesses and their customers.