I am a fan of the added funtionality for "Send Sample": being able to insert a lead's information in sample emails. Compared to the old functionality in which Sample emails only showed you blanks for default values in place of tokens, it is an advancement.
However, Marketo also tracks all the activity off the email and associates it with the lead... This is AWFUL!
Today we sent a test using a customer's lead info, and it logged the email as "Opened" on the lead record. I nearly had a heart attack.
If you have opens or clicks creating Activities or Interesting Moments in SFDC, and your sales people are anything like mine, they're likely going to call leads that they think opened or clicked, when in fact they didn't.
I encourage Marketo to look at testing options that allow for dynamic insertion of lead info into the sample without assocaiting the resulting activity off that email.