This launch is interesting. Together with Linux this will make the majority of cell phone platforms "open"*. I'm unsure if this was coming anyway (Nokia having some FLOSS sympathies) or as a catch up reaction to Google's Android platform. Certainly having an open platform makes it easier to get developer mind-share which is important when you want people to write the next generation of cool apps to put on your mobile device.
* Of course being an open platform doesn't currently mean anyone can write software for their mobile phone. However it is a stated aim of Android. It will be interesting to see if the handset manufacturers will see the light