Now that Blogsy has Posterous support, I figured I'd try it out. While I do like being able to mail in posts from my phone, composing posts on the iPad is easier with a good, dedicated client. So far, I really like it.
Attaching photos from Flickr or Picasa is drag-and-drop simple. Same with YouTube videos.
It's $4.99 in the App Store, and it's worth it if you lie to write longer posts on your iPad.