I honestly didn't read it closely, but apparently you didn't either. Your assertion:

   Given that the only difference between this and a normal 
   market is that a bunch of people offering to buy and/or
   sell at prices more favorable than the current inside
   bid/ask are banned from the market, I'm going to go out 
   on a limb and say that no, it won't help pricing very
   much.

compare that with:

   Since trading on Light Pool will be more expensive and 
   slower for those firms, they’re not likely to use the 
   ECN, reducing the negative selection investors 
   experience, Galinov said.

   Contributors, which will include long-term investors,
   will receive a “significant” rebate when they trade 
   against orders resting in Light Pool, while neutral
   firms, or those whose behavior falls between the other 
   groups, may or may not get one, Galinov said. 

So they are trying to get incentives right, rather than outright banning HFTs. Just slowing down the market may be sufficient, try reading this:

   http://ai.eecs.umich.edu/people/wellman/?p=40

(disclaimer: it's from my Ph.D. advisor, so I'm slightly biased)