While I do not see any real value in alternative cryptocurrencies, they can definitely be of value for trading. I made a considerable amount of money trading Namecoin, IXcoin, and i0coin when they first came out, but saw diminishing returns each time as the trading peaks and valleys became less and less severe.
I'll have to admit that I got things wrong with Solidcoin. This new currency obviously had more appeal to speculators than IXcoin and i0coin. Expecting Solidcoin to be dead in the water within half a day, I didn't bother touching it. Something happened, however, to spur its rise to a value even greater than Namecoin's. I believe the drop in Bitcoin's price had something to do with it, as miners and speculators quickly moved over to this new investment opportunity. Will Solidcoin last? I really don't think so. While it apparently has some properties that make it more appealing than Bitcoin, what it doesn't have is the history and infrastructure to truly make it take off. I give Solidcoin two weeks *max* before it vanishes into cryptocurrency history along with its stillborn brothers, IXcoin and i0coin.
***UPDATE***: The decline of Solidcoin is happening even quicker than I expected. Solidcoin's value has dropped from a high of 0.041BTC on Friday to 0.019 just 24 hours later.