As someone who doesn't use IE, I'm more impressed by a site saying "This site is only compatible with IE right now - we're working on it, though!" than with a s

As someone who doesn't use IE, I'm more impressed by a site saying "This site is only compatible with IE right now - we're working on it, though!" than with a site that is obviously broken and incompatible. And if you don't intend to ever make it work in the other browsers, say so up front. And users will figure out very quickly that it only works in IE; better to be up-front about it.