Hyascent's hourglass diffusers (you turn it once or twice a day, the scent drips from the top to the bottom and is diffused through the wood rings) are pretty darned good-looking, with a price to match ($169 at Neiman Marcus — only $11 less than the Diptyque version*). They last for about 6 months, and they say they are going to sell refills but there aren't any on their website yet. There are 9 scents, not one of which grabs me offhand but Bourbon Joy (vanilla, mandarin, cedar and muguet) or Bliss Me (fig, jasmine, violet leaf, vanilla and amberwood) might work for fall.

* Diptyque's Le Sablier comes with 75 ml of juice; the Hyascent comes with 180. No idea if they are of equal strength, though, so that might be misleading in terms of cost.