this video here shows some changes I made to achieve breath-taking performance. The last example is actually a grid view, with xaml cells, which in turn contain horizontal gridviews.
I've not put these back into xlabs as a pull request, and likely will in the mid-term future; but was wondering if anyone out there wanted me to blog about it as I have quite a few things I'm planning to blog about, and after blogging about Listview ViewCell performance thought I might tackle another subject (Ide extensions/embedding pages in pages); but the performance is so very good that I wanted to see if others have a need to know how do to this.
And in case you missed the blog post because you are not subscribed to the syntax is my ui newsletter (why the hell not!? 
) then here's the link.