Eurogamer attended Jack Buser's GDC talk "Developer opportunities in PlayStation Home" and came back with some pretty interesting stats on Sony's virtual world. While early reviews of the service were negative, Home seems to be enjoying a pretty large user base, if only due to its ubiquity.
Buser, Director of PlayStation Home in the U.S., claims that over 5 million people are using the service worldwide, with 2.2 million in North America. Additionally, visitors spend over 40 minutes per session in the world. He went on to say Sony plans to create, at minimum, three new "spaces" - Sony-built areas often used for promotional purposes - for inhabitants to explore each month.
Whether or not critics like the service, it appears Sony is invested in Home, at least for the medium term.