Just downloaded and installed the Squarespace iPad app. It works just like the iPhone app, just with more real-estate. So are it is performing as expected. It allows me to post right to my site, add photos to posts, add HTML, tags, etc.
I can also review posts on my blog and edit drafts or live posts. There are also analytics widgets to check site traffic and other measurement stuff that's important to bloggers
If you are a Squarespace blogger and have an iPad, pick up the free app. It's a no brainer.