You can choose from several blog designs plus you can customize 2 or 3 columns the way you want it. There are lots of customization choices that you will really like. For years, this has been a great set back from Blogger users. They have boring designs and a very minimal customizations. But this one is a great leap of Blogger.com.
All I can say is congratulations to Google for doing this. I think all is lacking is a more SE Optimization options similar to Wordpress.
Official Google Blog: Blogger Template Designer now available to everyone