Personally, I think “visitor” is the best choice out of all those suggested. This term would align with the metrics being collected on most websites, e.g. uniqure vistors, visits, etc. I do agree, however, that these folks are indeed “customers” that we are serving but that term does imply payment for a service, yet not so much as “client” does. Given this, I think it will still be hard to move us away from “user” but it is worth trying, as I believe the term does have negative connotations.