Notes: If you switch to a template like Simple and then add all of your snippets of code (like feed flare) then switch to Picture Window, you'll lose the snippets of code in the transition. Decide on a template and when you're sure you'll keep it for a while add in all the code back into the Edit HTML side.
If you've never added anything to the HTML side of your template then just ignore this post and play around with the new templates. They're a breeze to add to your blog and modify.
If you switch to the new Template Designer but want to go back to one of the plain templates go to Edit HTML> and scroll down to the bottom to find the links for the Layout Templates and the Classic Templates.