From their thingiverse page :
"A Sailfish is faster than a Marlin".Be sure to check their instruction before installing, but the procedure should be very easy.
Sailfish is the next generation of the Jetty Firmware. It's faster and has better print quality.
Supports: Replicator 1, ThingOMatic and Cupcake (TBA)
Firmware Manual: wiki.makerbot.com/jetty-firmware
This firmware contains many new features, some of which are: better acceleration, ditto printing, Pause@ZPos, SF50 Volumetric 5D printing.
Feature list: wiki.makerbot.com/jetty-firmware#toc3