The New York Times points out that in the conflict between House and Senate bills on requiring mental health coverage from insurers, it's a family affair:

A patient�s ability to get treatment at an affordable price often depends on state law. The National Conference of State Legislatures says that 42 states have some type of parity law.
The House bill says that federal law will not override "any state law that provides greater consumer protections, benefits," rights or remedies. The Senate bill, by contrast, would "supersede any provision of state law" that establishes standards different from the federal standards for cost-sharing and treatment limits.

Karen M. Ignagni, president of America�s Health Insurance Plans, praised this provision of the Senate bill, saying it would help "achieve consistency on how parity is defined" in different states.
But Senators Christopher J. Dodd, Democrat of Connecticut, and Bernard Sanders, independent of Vermont, expressed concern that the Senate bill could interfere with laws in their states.

Senator Kennedy said he was confident that he and his son could resolve their differences. �We will find ways of working together,� he said.

This actually clarifies something for me that had confused me in class -- whether federal legislation normally occupies the field (as the courts have found with ERISA), or merely sets a floor (as with the minimum wage). It appears that well written legislation says whether it's preempting state law or not. But given ERISA's field occupying tendencies, I'm not even sure how Rep. Patrick Kennedy's House bill would allow state law to stand. The 4th Circuit implied that ERISA's pretty much the defining legislation on employment benefits, so subsequent legislation that would allow state laws to push further than the feds on mental health insurance specifically, without allowing demands on employer spending on health benefits generally, seems like it could create some hateration, holleration between federal and state.