We have Parts 2 and 3 of the blog ready, just pacing out the publishing. BETA participation has been steadily climbing without us needing to market it, which is fantastic.
That said, the other blogs are on the media calendar, so just be a bit patient. Part 2 focuses on Domain Admin benefits, and Part 3 will have a HUGE list of end user features and changes.
All 3 blogs combined will essentially be the "features list" as they contain what are the biggest changes for anyone who interacts with SmarterMail. You can also see some of what's been happening by following the SmarterMail BETA category her in the Community.