In a word: nice. In more words: sweet, a patch that really does improve things. Most significant new feature for me is the additional media formats supported for playback. Now it really is as easy as bunging a bunch of DivX/Xvid/MPEG4/x264 files on a memory stick or external USB HDD, hooking it up to the beast and watching away. My only complaint would be a lack of Matroska (MKV) support, along with a lack of support for soft subtitles.
Along with the extra media support comes slight changes to the blades interface and original Xbox games added to the game store.