It's a bubble. Although I would expect GPU miners to switch to LTC when a lot of ASIC make it impossible to GPU-mine Bitcoins.
This will happen in the next month or two. Then I suspect there will be a crazy rush to switch over to LTC.
As an ASICMINER shareholder I've been following progress there and things are really beginning to ramp up. This will be followed by the Avalons and (eventually so I'm told) BFL.
For those who don't want to mine either currency and just want to buy in LTC is very cheap when compared to BTC even at todays rate so it has some promise of a good return for a comparatively low investment.
You can be an early adopter with LTC, to start trading BTC right now and expect to make any real return in the short term you need to spend tens of thousands of dollars.
I suspect a lot of new users will jump onto BTC, then see LTC and buy some anyway.