Dahlia, you ask with reference to the new FISA agreement : "Someone help me understand why it’s a good deal when one side gets everything it wants and the other side gets what it thought it had in the first place?"
Looking at this agreement, it seems to me that both sides got something, and both sides gave up something. Indeed, it looks like an ordinary civil-suit out-of-court settlement:
The Bush administration thought that its surveillance activities were lawful under the Constitution, the AUMG, and FISA itself, yet it agreed to bind itself to these new FISA procedures in order to eliminate the inter-branch equivalent of litigation risk. The president gave up discretion and gained certainty.
Similarly, Congress thought that its reading of FISA's applicability was the better one, yet it settled in order to eliminate the same "litigation risk." Congress got the president to commit to following these procedures, in order to maintain some degree of legislative and judicial involvement in the process.
Thus, in the end, both sides gave up something in the hopes of settling a dispute and reducing uncertainty.
Is it perfect? I suspect that neither side would say so. Is either party's compliance assured? No, because the president (Bush or his successors) may abandon the deal, or Congress (in this term or the future) may unilaterally amend the statute further.
But to say that the Bush administration "got everything it wants" and that Congress "got what it thought it had in the first place" is to wash a way a lot of the details and interests at stake.