Er, Josh? RTFM! < sorry, but I just couldn't resist >

I disagree with your statement "Unique indexes aren't maintained." From the help:

When a UNIQUE index or index tag is active and a duplicate record is changed in a manner that changes its index key, the index or index tag is updated. However, the next duplicate record with the original index key cannot be accessed or displayed until you reindex the file using REINDEX.