This is the biggest piece of good news from the WWDC. I have an iOS developer program license ($150 in Australia) and have been holding off on buying one for OS X until my app is mostly ready (why pay for it and let time tick by without having an app in the App Store?). Now I won't have to :-)
And to MildlyTangy (in reply to Cutting_Crew's post) yes, we have to pay, but only if we want to distribute apps through the App Store. We're free to build OS X apps and put them on the 'net for free, but to distribute an iOS app, there is no free method (unless you and all your users are into jailbreaking, which kinda limits your customer base!).