I have a particular fondness for Blogger and Blogspot because it is my first ever blogging experience. I signed up Blogger one night in October 2004 and like they said, the rest is history. So, I still keep my original blogspot for keepsake because I already had over 400 posts when I switched to my own domain and writing from Movable Type. Later on, I switched to WordPress.Org.
I had read and heard a lot of people lamenting about losing their template when they switched to Blogger Beta. However, I just pick up an announcement on Blogger about this new dashboard which will not affect our template.
With just one click I had switched a few of my blogspot blogs over. No loss of template nor sidebar links.
So, go ahead and do it! I have no guarantee though.