Their iPhone application seems to be doing well, though; today the folks at Joost announced that their free iPhone and iPod Touch application has been downloaded over one million times. It's not a record breaking figure in itself, but considering that Hulu still doesn't have an iPhone application (despite last year's rumors), Joost is at least ahead in this department. Their iPhone application has received a significant update lately, including several performance and stability fixes and a better interface.
It's not going to be enough to turn the tide, though. If you trust Compete's numbers, Hulu is way ahead of Joost (at least if you consider the website only, which is what Joost is now focusing on), and it's growing faster (see graph below.)