http://www.onlineregister.com/senseo/club/ -make sure you check the box that says “I would be willing to share my opinions as part of a Senseo® market research study”
This is the survey link they sent out to users recently, it had a specific email in it though, so it might not actually go through. I’d suggest signing up for the other link first:
http://www.onlineregister.com/senseo/survey/