Try this, if you can’t wait an official Froyo for your Epic 4G
Since Samsung and Sprint did not release an official Froyo for the Epic 4G yet so far, while you can’t wait any longer, please learn this instructions. The Epic 4G forums moderator, who discovers this approach, promises that this is an easy step to follow.
Epic 4G forums moderator ragnarox has taken the time to whip up a very comprehensive guide using some popular hacks that not only will get you your Froyo fix, but will put Samsung’s rfs file system to bed and replace it with the much snappier, and more reliable ext4 file system.
Featuring a 1GHz Cortex A8 Hummingbird Application Processor, the Epic 4G is one of the Galaxy S-series Android smart-phones. Running the new and improved TouchWiz 3.0 on top of Android 2.1, it has a LED flash, slide-out QWERTY hardware keyboard and supports the 4G network.
[via Android Central]