A good review, other than the fact that the article incorrectly places Posterous in the same [manufactured] niche as Tumblr. Posterous is just a blogging platform that lets you use existing technologies to author and publish posts (to various locations). I routinely publish hundreds of words to my Posterous blog, and nobody has reprimanded me thus far.
Yeah, i'm not happy when people think Posterous is microblogging or Tumbleblogging. There's no limit to what you can send us, and that's the beauty of email. Oh well, people can use us however they want, compare us to whatever they see fit. When people say they use Tumblr, I ask them how they post 3 photos, and they are stumped :)
Could you please reveal a bit of your future plans, for example what will be in the paid version? ;-) Or at least, I'd be very grateful if you can tell whether you are planing to allow displaying ads in the future.