Firstly you don't know how many watts it uses to mine scrypt, secondly this is early days (hours even). The original SC GPU miner is about 50% slower than what is available now. And future versions will likely extend that for SolidCoin.
As to scrypt, anything between 50% and 200% increase over what is there now wouldn't surprise me. You can pretty much kiss scrypt mining on CPU goodbye because unlike the custom SolidCoin algorithm it isn't a good all round choice for both GPUs and CPUs on a watt for watt basis.
That's... surprising. From what I recall, one of the things that was really slowing SolidCoin mining down on GPUs was writing to the scratch buffer. The SolidCoin algorithm writes to a small enough scratch buffer that it could be migrated to fast local GPU memory, though for some reason I'm not sure anyone's actually managed to do this yet. Scrypt writes its data to a buffer that's far too large to fit into GPU local storage.
The other curious thing is that the SolidCoin algorithm has some interesting time-space and logic-memory tradeoffs that Scrypt was specifically designed to block, and in theory they make FPGA mining of it a lot more feasible than it should be. I'm actually somewhat surprised ArtForz hasn't been FPGA mining it.