How does the experience of working at a "top" university differ from working at an average one? Being a professor at the top university in your field must be a very different experience from being a professor at a top 20 university, which must be a very different experience from working at a top 100, 500, etc. university. 

But how do these jobs differ? What are the qualitative differences between working at universities in different tiers? I'm less interested in pay and benefits -- more interested in the day to day experience.
(Since I've only been faculty in one department, my answer involves a bit of extrapolation...)


Quality of students — It is much easier for top departments to attract the strongest students to their PhD programs, so the average quality of students tends to be higher.  Faculty at top schools can spend less time bringing their PhD students up to speed and more time interacting with them as mature colleagues.  This has a big impact on the productivity, research quality, and enjoyment of the faculty.  (Of course, the strongest students are not all concentrated in the top few departments.)
Quality of faculty — Similarly, it is much easier for top departments to attract the top faculty in their respective subfields, so the average quality of faculty tends to be higher.  Again, this has a big impact on productivity, research quality, and quality of life.  (Again, the strongest researchers are not all concentrated in the top few departments.)
Rock star culture — See my previous answer about the benefits of being a PhD student in a top department.  The same comments apply to faculty in top departments. Of course everyone publishes in the top conferences and journals.  Of course every assistant professor gets a CAREER award.  Of course everyone has a few best paper awards.  Of course everyone sends their PhD students to academic positions in top departments.  Of course the faculty got another umpty-dozen-million dollars in grant money this year.  That's not exceptional at top places; that's just normal business.  That assumption of excellence is both incredibly powerful and incredibly stressful, just as it is for students.  Impostor Syndrome is rampant.
Center of the world — Top departments are more likely to attract the best researchers to visit, either as informal collaborators or as formally invited speakers.  This opens up many more avenues for collaboration.
Administrative support — Because top departments are well-funded, they tend to have more administrative resources.  For example, my business office (paid entirely by "indirect costs" from grants) takes care of all the financial and administrative details in my grant proposals, letting me concentrate entirely on the 15-page narrative.