The user response stuff is still one of those things most people aren't sure about. I think it's pretty clear that Google can collect a lot of user data and given they can collect it they're likely using the information in some way.
However how much that data is currently affecting where pages rank is still largely unknown. Our very own theGypsy (Dave)
wrote a post on the subject earlier today in response to a
Search Engine Watch post also from today. Dave doesn't really need me speaking for him, but his issue with the SEW post was that the info in it was presented as fact when it's still mostly opinion. I also know Dave has spent a lot of time looking at patents revolving around behavioral data.
I think it's fair to think that search engines will continue to collect behavioral data and when and where they find it useful and effective will use that data as a ranking factor. The jury is still out though on how much they might be doing at the moment.