SC is dead before it launched. It has too many drawbacks.
Now, the first alt currency I like and will probably speculate long on is "litecoin." It's like bitcoin, but using a CPU friendly algorithm. And without a ridiculous premine amount. It's intended to be the silver to bitcoin's gold and IMO it's the first alt chain with a shot of making it.
As far as impact? Short term positive, long term neutral. To speculate on the various shitcoins people need to buy up bitcoins. Those 2000 bitcoins up on the bid on btce are not in circulation, so every alt chain to come along is a slight, imperceptible boost to bitcoin price.
At least until that chain collapses.
Care to backup your points ? I think SC2 is great and Litecoin is crap.