I think this is yet another of those things where there is a real difference, but it's quite hard to identify as a listener - its more obvious to the player, and if you're aware of it, it will change how you perceive the tone you're producing when you play. To me it's more in the attack of the note than the sustained part, maple is 'snappier'.
The difference between ebony and rosewood is larger and is audible to a listener as well - even to the point that I think you can probably tell in a recording.
It's very easy to be dismissive and say none of these things make any difference - especially if you're going to use something like twanging an open B string in a non-musical way and recording it with a camcorder as "proof"

, but most players *know* there is a difference for a good reason, and it can be shown in a proper test.
I'd be the first to say that there are some parts of "accepted guitar wisdom" that are wrong, and can be shown to be so in a properly-done test, and others that are right even when the "technical" opinion says they shouldn't be... but you need to start off with an open mind, not an attitude.