If you look at altcoins as just testing coins with various parameters, then the more the better, maybe sometimes there can be important feature Bitcoin could use, but so far I dont see anything interesting in altcoins
When a kind of evolution mechanism gives us a better digital currency, sure. But just having the same core and adjusting the parameters, no. What is happening now is just ridiculous, a big waste of time, energy, and money. But a thing as Mastercoin is much more exciting.