It looks like TwentyXS is based closely on Twenty-Ten, or maybe Twenty-Eleven (other than header-image height Ten and Eleven seem a lot alike to me). What are the key differences between TwentyXS and whichever of the others you based it on?
There are over 1,500 themes and most of them are a variation or enhancement of another theme, making sorting and choosing very hard. I would love to see a standard practice of theme authors providing a feature matrix that compares their theme to its parents or other close relatives. Even if the feature matrix isn't comprehensive, it would be very helpful to see a "highlights" matrix that lists each feature that the new theme intentionally does differently than the old one.
I forgot (until I just saw it again) that you have a feature "infographic" on the theme homepage -- it's clever and useful, but it doesn't indicate which of those features are different from Twenty Ten. That's where a simple table/matrix would be helpful.