It's okay if you didn't. :)
I've just taken the plunge and switched over to a current generation Blogger template. The design probably doesn't look very different yet as I'm focused on transferring all the content over.
Why did I do it? I was using an old, highly customized template. I liked my template. I'd gone in and tweaked the code before the template had all of those options in the menu. But the code was such a jumble that I couldn't mess with it anymore. And the latest Blogger functions wouldn't work, which was frustrating. I could no longer find workarounds, but I couldn't use the ready-made versions either.
The funny thing is that I had created a 3-column blog before that was an option in Blogger. Now that they do offer it, I've gone back to 2 columns. :)
How I made the switch: I set up a dummy blog so I could work on the design before losing the old one. I also started to recreate everything in the sidebars, but got impatient and just copied/pasted some of it into Word to wait until I feel like entering the link lists item by item (it doesn't save correctly otherwise, which is annoying). Then I just cut and pasted the new template into my old blog. No back-ups or anything.
I did lose a few elements...
-my "Key Posts" list. Does anyone remember what should be on there? I'm trying to reconstruct it as best I can, but I know I'm missing something.
-my label cloud. I wish I had copied that code! The Blogger one isn't what I wanted and it's hard to find a hack with the code I need.
-how the blog looked in detail. I could have taken a screenshot or something. It's okay, though. My new blog is going to look a little different, I just liked the old one, too.
Anything else I might have forgotten to transfer?