I watch Xenscript (fighter's site for the mod) with great interest. The price for the mod is minimal for the potential it can provide.
At the moment, the main roadblock is its incompatibility with major WP addons that I use (and I suspect other sites use as well) such as Gravity Form, W3TC, etc.
I just can't wait to see some of the remaining issues resolved so we can take the next great steps.
Xen Porta is great and I think it has great potential but you can't compare it with the huge development and support community behind WP.