I think most of us like them, but since they are almost always outside of our control as to if we get one or what they will be, do players tend to let those titles inform their RP to a degree, or do you just treat them as sort of cosmetic fluff? Since custom longs seem to be far rarer, I'll leave those out of the discussion. And if you see someone with one, does it impact how you might interact with them?
I found that after getting one, a lot of the times it would cause me to altar my RP, or focus on it more. If only that people would sometimes reference it in talking to you, or ask the story behind it. So on some level I think they are great for promoting RP and should be a bit more common. On the other, you also want them to have some sort of meaning so that they do lead to that sort of RP engagement, instead of just being expected.
Some of my favorites were
Ireswyn the unfettered minstrel, but this one got overwritten when I became an enemy of the refuge which sucked.
Dwunot the Self-Proclaimed King of Silverwood, Cold-Hearted Gnome Murderer - This one really kicked up the RP for me since that was the char's whole role.
Kalisda The Sorrowful Siren of Sin - Scions and others started just referring to me as that, and it did help me push the RP a bit more, especially since this was one of my earlier characters and I was still getting into how to RP well with this one.
Xiersel, the Mistress of Creative Recruiting Techniques. Just cause it worked well for an empire bard and I did try to recruit people. I think the title came from offering a kitten to someone to join empire.
Oddly the only two noteworthy characters I ever played had titles I did not do much with. I think the title for Salyeris even made people think I was a romantic rep instead of a tragic, which was kind of funny. And Allysia's was my second favorite, but I'm not sure it affected the character's RP at all.