[stcredzero]

Another interesting thought: bullet-time would seem colder.

Yes, but then you also have friction and the required speedup of energy consumption and heat generation. Drag and friction increases with the square of velocity, so going ludicrously fast is going to generate ludicrous heat.

Also recall that there's an absolute zero. Basically, there's limited downside and much greater potential upside.

Interestingly, this would mean that you could have a civilization of Speedsters living comfortably inside a star.

Or on a Neutron Star, as in Robert Forward's Starquake. (With the speedup coming from the much greater speed of strong force mediated nuclear reactions.)