When I'm feeling manly there's not much better than 57% Smith & Cross neat
But I read somewhere long ago that the alcohol content begins to numb the taste buds at about 35%, and that around 60 deg. F. is optimal for release of flavors. I figure that dropping one small ice cube into a tasting sample, swirling it for 5-10 seconds, and then removing it with a non-metallic spoon, yields something reasonably close to those 35% and 60 deg. F targets. I'm far too impatient to measure out X ml of room temperature water.
When getting to know a new rum, I typically sample it that way and also neat.
I haven't really found a consistency as to which way tastes better.
But having convinced my friends that both ways are necessary, I get to drink twice as much rum

Students of the cask, reject naught but water. -Charles Gonoud, Faust Act 2