The folding GUI is an often neglected part of the IDE. It allows you to focus on the work at hand by hiding the unneeded parts of the code. What it didn't have so far in the NetBeans IDE was... style.
Actually style and an extra feature: the ability to close a fold by clicking at the end of it not just at the beginning. This is folding so far:
XHTML Renderer library provides us with way better looking HTML pages which can easily replace some of the Swing displays or make nice "preview" panels.
Furthermore, being included in the Platform, it's just a few clicks away to actually use it.