I love that it has an extra space, for an orange–or, I suppose, an olive, though I like to hope that the olive (symbolising a hope for peace in the Middle East) is a temporary addition, that it won’t be needed in years to come because there will be peace, and the orange (symbolising the fruitfulness of a fully inclusive Judaism) is a more permanent addition.
Of course, Aram’s designs aren’t always the best examples of halakhah-compliant ritual objects. The menorah my parents have drives me crazy because the branches are all at different heights. (This is a no-no.) So… it’s entirely possible that he just thought seven compartments looked nicer than the standard six. But since my seder plate usually looks like this:
My favourite seder plate, from a photo taken a few years ago. See how the orange is balanced on the spine of the book, there? And the salt water is in a dish off to the side? That is a seder plate with way more symbols than places to put them.
And since the orange and olive are both innovations, anyways, I’m not going to complain if this time the design blip works in my favour. (The menorah still really irritates me, though.)
 Of course, I feel obliged to note that according to Vanessa Ochs, Inventing Jewish Ritual, the actual origins of the orange custom are obscure, and Susannah Heschel seems to have no recollection of the legendary seder where the orange first appeared.