When using Ports, port 0 points to the Atmega's hardware I2C pins, but is still bit-banged. I remember I saw a blog post about a class template (?) witch allowed using the hardware I2C, but the code seems to be disappeared.
Normally the software I2C speed is not an issue, but I tried to use the Memory plug for storing some graphics, and could use faster speed. Of course it could be done with TWI library, but I'm too busy (and lazy) to write the code ;)