What we need are people actually setting up new goods and services for alt coins for them to take hold. However, even I only want to mess with bitcoin right now. The market hasn't accepted any other alt coin as a legit competitor just yet.
The problem is that if you set up a service that uses an alt-coin, you could get more users by opening it up to bitcoin. Alt coins need to provide something that bitcoin doesn't. Namecoin has names. Perhaps additional transaction types, or other experimental offerings.
Agreed, the main difference for the alt chains right now are the block times, or the mining/network specifics.
These aren't all that intriguing for a merchant who just wants to use any cryptocurrency. Because the merchants will want to accept a cryptocurrency that has the largest market (by number of users, not just market cap), which is bitcoin right now.
The advantages of "faster" confirmations probably isn't as exciting as people initially thought.
Also, I'm sure that the average merchant isn't gonna grasp many of the details of how CPU vs GPU makes a network safer, stronger, etc.
Either way, the idea of merged mining is still interesting because it allows us to transition in the future to another option (probably yet to be created) that comes up with something really attractive.
For that we can thank nmc,ixc,i0c,dvc. We'll see if they come up with anything else to attract market attention.