'Diminishing returns' rather than 'incremental', since speed multiplier increase at prestige is capped by completed missions (x1.5/x2/x3 with ending), and missions are limited in number. This obviously becomes a smaller and smaller percentage of your already accumulated speed multiplier as the game goes on.
Prestige after 6 hours, so the next run will be 2% faster, and the next one after that 1.8% faster (or whatever)? Not a lot of incentive to keep playing.
Otherwise all the progress bars are satisfying enough for a while.
A shortcut, like ctrl-clicking on a tech, to upgrade to next milestone would save a LOT of annoying clicking. (Click tech, make sure NXT is being bought, click to upgrade, click somewhere to hide the buy UI, repeat...)
 "Idle Quest"){kind=icon}
![Play Idle Tech Tree - [Early Access]](https://cdn4.kongcdn.com/game_icons/0069/0630/game-icon.png?i10c=img.resize(width:250) "Idle Tech Tree - [Early Access]"){kind=icon}
Hey, that's a great idea - let me add that to the to-do list. EDIT: Done for tonight's release :-)