Total_Noob told me a few days ago that the Hen was very close to completion, and he confirmed that in a post on the german site pspking.de. He announced that his Hen now has 98% homebrew compatibility, a VSH menu (probably similar to what we have on the m33 and Gen CFW), and a “NanGuard” feature, which will prevent people from stupidly writing stuff to the flash.
source PSPKing.de (thanks to Ah-Chai and Mark for the tip!)
Last time I spoke to Total_Noob, there were still a few thing to finalize and a few bugs to fix, such as unlocking the 32MB of extended memory on models that support it.
Note that although Total_Noob announced that his Hen will not have ISO support, several teams are already actively working on game Loaders (such as Open Idea Iso Loader by dridri, which supposedly loads ISO/CSO and PSX games). Such loaders will probably be made compatible with firmwares 6.xx with little effort, and I am more and more confident that it will be a matter of days after the release of the Hen before things such as iso loading or plugin support are made available.
A Hen (Homebrew ENabler) is a tool that allows to run unsigned software (homebrews) on a PSP directly from the XMB. By default a HEn only allows homebrew loading (even though Total_Noob pushed the limits a bit further by adding features such as a VSH menu) and is not very different in its goals from a tool such as HBL. But unlike HBL, it relies on a Kernel exploit, which basically gives access to all the features of the PSP. It allows users to get full control of their psp, for better or for worse.