I finally downloaded 10 Premium today, but I am having massive problems with it.
Firstly, it won't let me create a variant, each time I get the error message "Internal Program Error 1620.k.No.AR". I figured the reason might be that the width of my website is actually far beyond the usual 760px. I then reduced all pages to 760. I could create the variant, but it messed up the main site:

I have different pasteboard backgrounds on the original site, but after changing the page size all pasteboard backgrounds are the same. Not sure if this can be changed, I am giving up after an afternoon of trying.
Also, I cannot have different page lenghts any more. Any changes to page length applies now to all pages. This is very confusing and extremely frustrating.

I will give it another shot, but maybe just stick with version 9 until all problems are sorted.