I just wanted to toss you hard working folks a quick Kudo; I just upgraded my Treasures site from 1.2.6 to 1.3.0 and it went well. Didn't blow anything up at all this time!
I used Winmerge (as you suggested) to find and transfer my customizations into the 1.3 files, uploaded and ran the Update Database function.
I really like the new features, especially that Page 1, Page 2, Page 3 now show the page titles. That will save a lot of work. And I like the new fonts.
Next I will work on the Smoky Mountain Woodworks site, but that one embraces MASSIVE format changes and will take a long time to merge.
Thanks for the great upgrade!
Your new site looks great, by the way.