BitBucket project link: http://bitbucket.org/artvandalay/mercurialpsprovider/
The big user-visible change this time is the optional parameter -HgExtraParameters. In practice someone would probably use a shortened form like "-hgextra". This parameter is for additional hg parameters when the command returns something other than changesets and therefore -Filter doesn't apply. If you're getting a changeset's content, which is its diff against its first parent, you could include -hgextra "--reverse" after the path to instead see a diff that reverses the changeset.
Underneath, the changeset cache has also gotten smarter since 1.6.8. It now remembers the exact identifiers that have resulted in each changeset in the cache. This means that when a relatively strange identifier like "-1" yields a cache miss but a successful result from Mercurial, the same identifier will pull from the cache from then on. If Mercurial can figure out how to link a particular identifier with a particular changeset, then the cache will "learn" that.
The other minor performance enhancement is the addition of a one-entry "command" cache. The last hg command executed, and its result, is stored. When the same command would've run multiple times in a row, only to get the same output each time, now it will only need to run once for the sequence. Given the caching already present at the level of changesets and changeset manifests, the primary benefit to this command cache is speeding up when a command fails. When this happens, the Provider infrastructure appears to rerun the failed command five times. The command cache allows for the command to fail faster each time...