All alt coins besides litecoin are definitely in an infancy state with none having a huge lead on the other imo.
I can certainly agree with that, especially since most of them are only a few months old.
I have been watching some of the other coins such as Digital Coin and World Coin and they do have more infrastructure than Gold Coin. Nevertheless, their "Ebay" clone sites hardly have any activity from what I have observed. It may take much patience and time for a coin to grow and become accepted.
I like the idea of gold dealers using GLD as a means to buy gold, silver, platinum or palladium coins. This would in effect give GLD an implicit gold backing, because you could exchange it at any time for cold hard cash. At this time, however, the entire amount of GLD in circulation can only buy 5 or 6 ounces. Perhaps we can focus more on GLD usefulness in July after the new client is released.