MacHg is a native OSX GUI client for Mercurial. It is modern and fully multi-threaded using Grand Central Dispatch and threading goodness. It has a clean interface and allows multiple repositories per document, using a standard mac sidebar interface. It incrementally loads data so its very fast. Ie it easily handles browsing the mozilla repository which is 3.35Gb. MacHg is fully featured handling all standard Mercurial commands, and additionally provides history editing features through the Mercurial rebase, strip, collapse, and histedit extensions.
Mac OS X 10.6