The iPad has been out for nearly a year and a half and Sony is joining the game really late. Other companies rushed their design processes to get a tablet to consumers and have failed relative to Apple and its iPad. Really the only thing the iPad is missing (for me) is portability, I rarely take it out of my office or home. Sony and the S2 may solve this issue with seamless operability much like a single screened tablet.
The Sony S1 is expected to have a fall 2011 launch for the Wi-Fi version, and the S2 will have WiFi enabled along with AT&T's 4G network.