I think that there's a lot of dissatisfaction with the "atheist" label generally -- I've been in a couple of focus groups and I wasn't the only person expression frustration at, for example, being defined negatively or by absence.

I have a quantity of colleagues for whom their faith is pretty all penetrating, and it the major tool they use for interacting with the world, defining their own morality, investigating society, etc. If you look at faith from that perspective, i.e. what do I use to set the rules, what do I measure goodness against, what defines fairness, rightness, fitness -- then I have a fairly obvious descriptor. I am a "scientific rationalist" -- I use science and reason to inform my interactions with society and the world. However, language and usage mean that there's a lot of judgement embedded in that term, and it's not at all polite to other people of other religions! I would opt for the far more -- well, utilitarian "utilitarian".

The focus groups, incidentally, are likely to lead to a "no religion" tick-box or similar.