SMS messaging in the US on the upswing

According to this article, SMS messaging is becoming more popular in the US, with 35% of US mobile phone users serveyed reporting that they regularly send SMS messages, compared to 70% of UK users.

Another interesting stat is that 8% of US users regularly send picture messages, compated to 15% of UK users. I'm VERY interested in picture messaging popularity, so this is a statistic to watch.

If you know of any other recent studies that describe messaging trends (SMS, pictures, etc.) please post URLs. Thanks!