My DD is Eloise, and she is the only one at her school. I like it because it is unusual, but not too off the wall.
The main reason I like the name is because there is no 'Eloise' type! I think the name has a modern feel, yet dates back to the 14th Century. There was an Eloise on the Titanic, I have taught a few Eloises (who would now be in their teens and early twenties), and of course it remains just outside the top 100 (and has never gone higher than the top 90 since 1998).
Not only that, but it is also in many ways, classless. Unlike the previous poster - Eloise is not a chav name, unless of course royalty counts as chavs . Representing the posh end -there's Lady Eloise Anson, Countess Eloise (granddaughter of the Queen of the Netherlands) and Eloise Taylor, daughter of Lady Helen Taylor, but then again you get the ordinary Eloises too. I've read people on here describing the name both as common, but also as posh!
As I said, one of the great appeals of the name to me is that as a name, it is like Katherine or Elizabeth (albeit less popular), in that when you hear the name, you cannot assume the type of person you are going to meet!