Since I have hundreds of ships, I use specific shipnames for specific fits. Additionally, I use prefixes as an RP tool.
As an RP tool it is pretty effective because it is very visible. I sometimes see enemies using the TES designation as well, only usually with some kind of insult attached to it, and often by non-RPers.
However, that shows people take notice of the prefix, and they remember it and associate it with a specific kind of faction (in this case the Amarr). To me that is excellent use of a small RP tool. You are building an image and therefore helping to build the world.
As for myself, I'd like to think that when people seem TES Silver Templar on scan, they know if they should run or not, because they know what they'll likely be facing. And if people are smart enough to realize that when they see TES Purple Templar that they are actually facing a different setup, all the more power to them!