...what about a feather duster?
Negative on the feather duster, you don't want to touch the driver unless absolutely necessary, as the oils from the duster, or anything else (IE - your hands) can potentially break down the epoxy coating on the driver
As an owner of a set of L710's, I know how irritating it can be to look at a dusty dome driver, but there is nothing you can really do about it, except replace the driver dome. It is also true that it doesn't affect the sound.
I have tried several different ideas on damaged ADS tweeters, and all have failed. They have a strange type of epoxy that is forever sticky, and unless you have pet hair, leaves, or a large foreign object attached to the driver, you shouldn't try to clean them. A previous poster is correct in saying that the dust doesn't affect the sound, including the incredible imaging that these speakers are capable of creating when properly placed.
My best solution to this problem is to leave the grills on (if you have them) as much as possible, as the metal ones (if you have that style) have small enough holes that dust really doesn't get through the perforations in the grill, and as for the cloth ones (like I have), the fabric stops the dust entirely. The only time I take the covers off is to service the drivers or to quickly blow the dust off of them in the garage.
-Jason