Even after 100 times, I found it counter-intuitive and irritating that clicking "New Post" on my site would launch my email client instead of their editor. The latter is buried somewhere in Settings.
Then when I posted it, it grouped all the pictures together.
We're changing our "post" links to all go to the web editor. While email is still the #1 way our users post to posterous, those already on the web want to stay on the web.
For images: we default to grouping them together into a gallery. But you can also separate them out into individual photos.
-Sachin CEO, Posterous
1 thing i am dying to see in posterous is "preview" option plus the pages & link section is a littile clumsy.