Premium members can now save posts as a draft before they post.
You should see a "Save as Draft" button next to the preview button when your writing a post. You can see your drafts in your profile.
My Profile -> Profile Info -> Show Posts -> Drafts (edit a draft to post where you originally saved it).
* Three-Socks runs away before the revolt.
Seriously though its the only good perk I can offer premium members for now. I know you would of joined premium as a way of donating and keeping this site running for everyone. So its just a little bonus for your generosity