I agree with most above. First of all, this program was fairly short-lived, didn't they just introduce it a year or so ago?
I have used the domestic companion program several times for great deals - the best being when United quoted me in the neighborhood of $470/person for IAD-SFO over a random weekend for a wedding, and the domestic companion program got us BOTH tickets for $420 total, all-in.
I also agree that the international companion program is almost completely worthless. I've never had them quote me flights that were anywhere near the price of simply paying for two business tickets directly from the the airline, much less a consolidator.
$500 a year for two cards is getting harder and harder to justify.