It's not like the second processor ONLY gets used when a program is written for it, it is used quite often actually. One program will run one processor and another could run on the 2nd processor. This is good for things that are CPU intensive but aren't written for dual processors; it enables you to multitask when you normally can't. For instance, you can encode a movie with Gordian Knot and also run your computer with the normal tasks all at once. Or, when a system is very well setup, you can run two intensive tasks at once, i.e., you can play a game and encode MP3s in the background for instance. Though very expensive, I think they are worth the money (I do not have one, but I use them every so often), even when you don't run optimized programs.
Damn Rambus.