I wanted to give you an update on our progress on this test and analysis.
The winner looks to be not requiring any matches for first name (same as current default), but using the phonetic algorithm on last name rather than Soundex.
We've rolled a larger percentage of new search users (US site only) into what we believe to be an improved default setting based on our analysis of the test data. We'll track that information for a while to verify that it performs as we expect it to.
I'll post more here as we complete the roll-out.