I'm excited to hear that the UI might be refreshed / redesigned. In my opinion, the PP products are overdue for an update to the look, which could help bring a more "web 2.0" type look. Something cleaner, with less visible lines, borders, tables, etc. Clean is nice.
With that said, I'm disappointed to hear that this might involve Javascript and AJAX. I don't really have a problem with them but if you add too much code you're going to slow down my 7 installations of your products.
Google has already publicly stated that faster sites get a boost in rankings with all else being equal.
So don't go overboard on the scripts for the presentation and extra features. Or, offer the option to enable all these extra
JS/AJAX scripts, social sharing buttons, etc. Have the "base" install as a good, clean, fast-loading code templates. I care more about a fast site than I do a fancy looking one. And so does Google.