I had a similar experience. I was working thanksgiving evening and sent them an e-mail complimenting their unique advertisements (weird, I know - I'm graphic artist though, so I really appreciate the creativity that goes into most of their ads). I got an e-mail back a few minutes later, from the cfo. I was blown away, and actually felt kinda bad for e-mailing on a holiday!

I never expected a response at all, let alone that night.