litecoin seems to trade pretty much like btc. It doesn't seem to have any personality of its own. Hopefully it will get a boost when it is on mtgox soon but we'll see.
LTC is the same as BTC with another algorhithm.
It is pretty much resistant to contemporary miner designs, which makes it a "people's choice" kind of.
Competition is good. The apps look the same and theoretically, a combined wallet software could store all kinds of different cryptocoins. It isn't that hard. Just as you would pay with dollar, Euro or Yen, you could probably decide to pay in whatever currency you want, as long as the same basic transaction mechanisms are kept similar.
it's good to diversify. 
