The primary draw here is likely the ability to access Hulu content on devices such as the iPhone (3GS, iPhone4), iPad, iPod Touch (3rd Generation), and Samsung Internet TV's and Blu-Ray Players. Future support is promised for Internet-enabled Sony and Vizio TV's and Blu-Ray players, as well as the PlayStation 3 and Xbox 360. For the consoles, PS3 support is coming in July, while Xbox 360 owners will have to wait until "early 2011" and it will require an Xbox Live Gold subscription.
Full seasons of television shows will be available during their current runs. On the web, using the boring-old, free, ad-supported service only a small subset of current episodes are available due to licensing reasons and they are largely delayed. The monthly fee destroys this barrier opening up all of the content for your enjoyment. If you don't have cable or satellite, this is probably a great way to check out some television shows.
After a quick glance, it appears that some of what is available on Hulu Plus is available on the Hulu website when it comes to shows not currently airing. For shows that still live on, Hulu Plus will net subscribers full collections in most cases. What Hulu Plus does not have, however, are any of the feature films available on the website.
While the service is currently only open via invite, interested parties can request an invite. Like Hulu, this is only available in the United States.