For better or worse, regulation NMS is scheduled to be fully implemented in July, and you have to think it will be a pretty big deal. But ensuring the best price for every order is basically a technology greased endeavor, and the challenge will be a bit different for every exchange. Goldman Sachs analyst Joshua R. Carter thinks that the regulations are good for the Nasdaq, and not so good for NYSE Euronext. The Nasdaq's dealer-driven, computerized approach is better positioned for the new rules. Carter expects NYSE's market share to continue to erode. He even slashed his 2007-2009 estimates by 8 percent each year on average. Meanwhile, he boosted his 2007-2009 estimate for Nasdaq by 6 percent on average.

For more:
- here's an AP article