I2C in a Nutshell
I really don't like I2C. Yes, in principle it's pretty simple, but if you consider NACKS, slaves holding SCK low, what happens if your master resets while the slave is trying to send a 0 bit (hint: power cycle!), etc, it's so easy for the peripheral to get stuck.SPI is much easier to write correctly, and pretty much only has the extra wire (usually not a problem) and the phase polarity issues as a negative point.