The main problem with "rationalist" is that instead of declaring one's goal, one seems to be claiming to have achieved a goal. To most people it seems arrogant. So I like "truth seeker" because it so clearly avoids that problem. Of course "truth seeker" also has the problem that it implicitly accuses everyone else of not seeking truth. Believe me, most people understand this slight and are not happy with it. So which insults other folks less - saying we love truth when they don't, or saying we are better at finding truth than they are?
Actually, a broader view of this seems useful. Any time we say "I am an X", the person you're talking to is likely to take it as you implying that they're not an X, unless they already identify as being an X as well. So any good-sounding X will come off as insulting. A bad-sounding but interesting X might be useful, but that seems prone to backfiring, and neutral values of X are both difficult to construct and not very stable.
Stating it as 'I do X' or even 'I do X well' seems more likely to be taken well - there's less of an intrinsic implication about whether the other person does X.
I've noticed that here on Less Wrong people often identify themselves as rationalists (and this community as a rationalist one -- searching for 'rationalist' on the site returns exactly 1000 hits). I'm a bit concerned that this label may work against our favour.
Paul Graham recently wrote a nice essay Keep Your Identity Small in which he argued that identifying yourself with a label tends to work against reasonable -- rational, you might say -- disscusions about topics that are related to it. The essay is quite short and if you haven't read it I highly reccommend doing so.
If his argument is correct, then identifying with a label like Rationalist may impede your ability to be rational.
My thinking is that once you identify yourself as an X, you have a tendancy to evaluate ideas and courses of action in terms of how similar or different they appear to your prototypical notion of that label - as a shortcut for genuinely thinking about them and instead of evaluating them on their own merits.
Aside from the effect such a label may have on our own thinking, the term 'rationalist' may be bad PR. In the wider world 'rational' tends to be a bit of a dirty word. It has a lot of negative connotations.
Outside communities like this one, presenting yourself a rationalist is likely to get other people off on the wrong foot. In many people's minds, it'd strike you out before you'd even said anything. It's a great way for them to pigeonhole you.
And we should be interested in embracing the wider world and communicating our views to others.
If I was to describe what we're about, I'd probably say something like that we're interested in knowing the truth, and want to avoid deluding ourselves about anything, as much as either of these things are possible. So we're studying how to be less wrong. I'm not sure I'd use any particular label in my description.
Interestingly, those goals I described us in terms of -- wanting truth, wanting to avoid deluding ourselves -- are not really what separates "us" from "them". I think the actual difference is that we are simply more aware of the fact that there are many ways our thinking can be wrong and lead us astray.
Many people really are -- or at least start out -- interested in the truth, but get led astray by flawed thinking because they're not aware that it is flawed. Because flawed thinking begets flawed beliefs, the process can lead people onto systematic paths away from truth seeking. But I don't think even those people set out in the first place to get away from the truth.
The knowledge our community has, of ways that thinking can lead us astray, is an important thing we have to offer, and something that we should try to communicate to others. And I actually think a lot of people would be receptive to it, presented in the right way.