When upgrading from 2.0.7 to 2.1 (or, for that matter, from 1.5 to 2.1), is it necessary to upload the 'themes' folder? I have made a lot of changes to the 'default' theme in previous versions.
Obviously, if I upload the new themes, the design of my site will be altered and I will lose my changes.
On the other hand, I am worried that by not uploading the themes included with 2.1 I am missing a new feature or security.
I don't even know if the code for the theme pages changes from 1.5 to 2.0 to 2.1.
What is the safest thing to do?
edit: fixed mispelling in topic name