Unlike streaming solutions from Roku and Microsoft's Xbox 360, Boxee's effort includes the option to both browse and search through Netflix's library. Roku's box and the Xbox are currently limited to showing users the videos from their saved queues. The two also require special hardware (and in the Xbox's case a paid Xbox Live Gold membership), whereas Boxee works on any Intel-Mac or Linux PC. Boxee's service is not yet available for Windows.
Another caveat: Netflix streaming is not yet available for the AppleTV version of Boxee. I'm told the main reason is that Microsoft Silverlight, which is what Netflix uses as a delivery method for its streaming content, has hardware requirements roughly double that of the processor inside the AppleTV. Silverlight requires a 1.83GHz dual-core Intel processor, while the AppleTV only sports a 1GHz "Crofton" processor--a derivative of the Pentium M.
Along with Netflix support, Boxee now links up with MTV to pop up music videos for any songs in your library that it can match. There's also support for YouTube videos that have been encoded in h.264, and new player interfaces for Hulu, CNN, Picasa, YouTube, and Flickr. The updated UI offers slightly more streamlined playback controls, solving one of my big quibbles with the last release, which actually kept you from being to skip around a video's timeline in Hulu and CBS videos.
Existing Boxee users should get an update notice when firing up the app later Thursday. The service remains in private alpha. You can sign up for it here.