Once you download the app, there is a remastered version of the Svanslφs cursor set created by Max Rudberg which is retina-screen ready.
Mousecape is as non-instrusive as possible, never asking you for your password for anything. It works by using private APIs created by Apple to register system cursors so it has no performance hit at all.
Capes, or cursor sets, are applied for as long as display state doesn't change, meaning until you change resolution, monitors, sleep your computer, reboot or logout. However, inside of the application is a helper application that will detect when the cape is reset and will apply it again.
Mousecape is available for free, open source and with no obligations. Users can create and share their own capes that are animated and bring new flair to the operating system.
[crarko adds: For 10.8+, including Yosemite.]