I agree - asking for contemporaneous feedback is key. It will not only be more accurate than someone's recollection later, it will also be tied to a transaction

I agree - asking for contemporaneous feedback is key. It will not only be more accurate than someone's recollection later, it will also be tied to a transaction or other logs and can be compared and analyzed with other transactions. It's important that the feedback doesn't take your user out of the flow. No popup windows, no long surveys.