Apple is an innovative company; but in a different way. Rather than developing entirely new product categories, it excels at taking existing, half-baked ideas and showing the rest how to do it properly. Macintosh was not the first PC (remember Steve Jobs visit to Xerox PARC?), iPod was not the first MP3 player; neither iPhone was the first smart phone. Same is true for iPad.
But something is also different since iPod. Apple provides a vertical business opportunity for small players; basically everyone can become a big player in this model. Unknown artists can sell their songs without going through big production companies. A kid can create the best application for iPhone and compete with major software development companies. I guess same is going to happen for iPad.
Open source and its community were out there for a while. But big organizations (Nokia, Microsoft, …) were worry to lose their dominance. Nokia open source model was not successful for its smartphones because it did not provide real vertical for geeky developer to create revenue. Still Nokia was a big corporation and could not see someone out of its system makes some money. You need to be a part of the system! Apple on the other hand has its rebellious attitude. Lets provide SDK for free and let the guys create revenue. Use its huge marketing muscle and create an avenue for smaller players. It broke the dominance of mobile phone companies and their dominance in software for smartphones. Probably this is the time for PC software companies to be afraid!