The biggest complaint I hear from non waze users is that it routes you a zig zag through a neighborhood or takes you off/on the highway to save 20 seconds.. I use it everywhere I go myself, still worth it BUT I do get annoyed when a significant amount of twists and turns if they don't end up being necessary.

I suggest a slider in settings in which the user could say "keep me on the most direct route unless it saves me at least" 3 minutes.. 5 minutes.. 10 minutes etc.

In order words allow me to set my time saved tolerance and if I set it to 3 minutes for example keep me on the highway unless getting off and back on will save me more time than my tolerance setting.