As described in http://www.raspberrypi.org/archives/1929, there are various changes. Does this affect software that isn't using I2C or the new GPIO signals? I'm assuming I wouldn't be using the emulator or JTAG.
Nothing at that URL indicates that there should be any software changes if you are not using the GPIOs - however there is sure to be something they overlooked. We'll just have to wait until someone finds it :)
They've swapped the I²C connectors.
For I²C, this just means you need to check the revision in
/proc/cpuinfo and use
/dev/i2c-1 as required.
Or you can use
i2cdetect to look at both busses for any devices you are trying to talk to.
If you are using the I²C pins as GPIO, it's a bit worse because if you are using a GPIO library you'll have to make sure it's recent enough to check
/proc/cpuinfo and remap those pins.
The good news for some is that the 4 pins that were to be used to indicate board versions can now be soldered to and used as GPIO if you need some extra :)
No, this should not affect software that isn't using I2C or the new GPIO signals.
If you are using I2C or the GPIOs, you may need to make minor changes, but careful programming should mean that the same binary will work on both revisions. All other software is unaffected.