I just picked up an XD45ACP for $499...not a great price, but not bad at all.
$540 is pushing it a bit, unless instant gratification (Assuming your state doesn't have some kind of waiting period) makes it worth your while.
The only reason I haven't chimed in on this thread is because I haven't actually shot it yet
However, it fits my hand fantastically. Totally ambi mag release without modification (I'm a righty, but you never know), it points naturally, and it has what I consider a necessary thing; a grip safety for a handgun that is designed to be carried loaded and cocked. Think Glock, but with that added measure of "you must actually be gripping the thing like you mean to shoot it for it to go off" safety. And it's rail accepts Glock accessories as well as other accessories.
No, I have NOT touched the Smith. It didn't really interest me, truth be told. So, I can't comment much on that, other than to say I'd like to give the Smith a try, as well, just to see.