With Uber though, they specifically instruct that a normal, decent ride should be considered a 5. Does this still work when most users rate most rides a 5?
Once you know the user's average/variation, you can normalize it in any way you want. If you think that the "average user experience" merits a 5, you can do that as well. The downside of course, is that the above-average drivers don't get any recognition at all for going the extra mile.