All memory bandwidth intensive "professional" computing (that I know of - rendering, encoding, simulation) are being done on (or quickly being moved to) GPUs these days. And those GPUs sit in racks, not under the desk (and guess what, the GPUs have ECC! ). Standard memory performance is simply not an issue for these types of applications.
My point was that gaming is the only use I can think of where it's important to have a fast machine sitting next to you, and the X58's triple channel bandwidth was already overkill there. Even if you run renders or whatnot on your desktop, having the ECC insurance against a wasted overnight run is way more important than finishing an hour earlier.
That's debatable. It's hard to really determine how many crashes ECC really saves you from.