With over 2 million sold the news of a RPi upgrade is big news. The basic specs haven't changed much, same BC2835 and 512MB of RAM and the $35 price tag. There are now four USB ports which means you don't need a hub to work with a mouse, keyboard and WiFi dongle. The GPIO has been expanded to 40 pins but don't worry you can plug your old boards and cables into the lefthand part of the connector and its backward compatible. As well as some additional general purpose lines there are two designated for use with I2C EEPROM. When the Pi boots it will look for custom EEPROMs on these lines and optionally use them to load Linux drivers or setup expansion boards. What this means is that expansion boards can now include identity chips that when the board is connected configures the Pi to make use of them — no more manual customization.
The change to a micro SD socket is nice, unless you happen to have lots of spare full size SD cards around. It is also claimed that the power requirements have dropped by half to one watt which brings the model B into the same power consumption area as the model A. This probably still isn't low enough for some applications and the forums are no doubt going to be in full flow working out how to reduce the power even further.
There are some other minor changes, comp video is now available on the audio jack and the audio quality has been improved. But one big step for Raspberry Pi is that it now has four holes for mounting in standard enclosures — this really lets the Pi go anywhere.