We love the 'Send Sample' email for a perticular lead. That helps us to pinpoint and validate personalizations and dynamic contents are correctly populated in our emails for multiple scenarios.
It would be great if there is a 'Preview Sample' for a landing page for a perticular lead. That will help us to validate dynamic contents, and more importantly for us, rendering of landing pages in different scenarios of progressive profiling based on how complete or incomplete the lead's profile is in our database.
Technically there might be some cookie etc based limitations etc to make it happen. May be 'incognito' browsing mode might help. Is this functionality in the roadmap?
If not, I was thinking of creating a framework in our Marketo instance and API etc to implement this as a tool for me.