I will be upgrading to one of the new Blogger templates today. It says there are new features, so hopefully "features" are good things and not bad. Some of my current blog items (such as archives, blog lists and such) may disappear for a bit. Have no fear, I have saved my old template and should be able to add them in later.
For those of you who are considering making the switch to Bloggers beta version, I will post as much as can of my experience. So far, I have had no serious issues. The only thing I have found is that you cannot use a Blogger account that has been converted to the beta version to sign posts on non-beta blogs. This means that if a blog absolutely requires blogger accounts for comment posting, you are out of luck. Fortunately for me, most of the blogs I read do not have such a requirement. If you wish to comment on a non-beta blog, you can simply use the "other account" type of comment login.