TheMadScientist - 2:58 pm on Nov 11, 2012 (gmt 0) [edited by: Robert_Charlton at 7:11 pm (utc) on Nov 11, 2012]
Whether the URLs that are 302 rather than 301 are replaced or not, the visitor ends up in the right place and, IMO, the ranking will not change with the replacement of the URL in the SERPs. (They will be replaced).
404s which were indexed will continue to be indexed for a period of time, because it's 'not found' which means it could be present again, but they will be removed.
410s are not indexed at all and you lose all inbound link weight, age and other associated information with the page, so in this case, the suggestion to use a 410, IMO, is completely incorrect ...
[edited by: Robert_Charlton at 7:11 pm (utc) on Nov 11, 2012]