Search engine features research?

[Sheva]

As I had previously stated in another topic, I am working on my dissertation about search engines. It has been fun so far if a little complicated.
I was hoping to conduct a survey on the search engine features that the users appreciate most, however due to time constraints, I am unable to do that. Instead, I have decided to use results from some other research. What I need is the approval of features that are highly regarded by users. I mean all of us know that, speed, relevant results, clean interface/user-friendliness are what we like but since this is a dissertation I can not take this for granted and I have to back it with a research.
Can I ask everyone if you have ever come across such a study or news item? I'll be very grateful to anyone who can provide me with some help, thanks a lot in advance..