> If they get you there without incident and don't annoy you too much that seems like a 5/5.

Here's how the scale I instinctively would use would work: Getting me there without incident and without being too annoying would be a 3. If they don't annoy me at all, that would be a 4. If they do anything that makes my trip better (a better route, a good, relevant suggestion for where to go for something of interest to me, or just making my day a bit brighter), that would be a 5.

Problem of definitions. Personally I don't want any chit chat, so what makes a ride a five for you lowers it for me. At the end of the day I just give service people top marks unless they did something terribly wrong.

Yes, that's the underlying issue with simplistic rating systems like 5-stars -- different people value different things. Even if we all agreed on some standard like "average == 3 stars", everybody has different desires, so my 5-star ride may only be a 3-star for you, and vice-versa.

My favorite Uber ride was in a party van. Great way to get home after long trip at night. In an ideal system I think they'd be a 5/5 while most of my other rides would be 4/5.

A while ago the story went around of an Uber driver who hooked up a Nintendo Switch with Mario Kart in the back seat.

That guy probably deserved a "true" 5-star rating.