I've already reviews Sabayon 5.2 and 5.3 KDE, so I don't think it's necessary to repeat the history and roots of Sabayon. Suffice it to say that it's an easy-to-use binary variant of Gentoo that includes everything and the kitchen sink.
According to the Sabayon developers, Sabayon 5.4 brings to the table a new theme, many bugs fixed, and a couple changes in the included applications. Follow the jump to see how it fares. I tested this in VirtualBox with 1024 MB of RAM allocated for the guest OS, as this is how much RAM my old computer had when I tested Sabayon 5.2 on it directly (i.e. from a live USB instead of from VirtualBox).