Slide 40:
Advantages
Full duplex communication
Higher throughput than I²C or SMBus
Complete protocol flexibility for the bits transferred
Not limited to 8-bit words
Arbitrary choice of message size, content, and purpose
Extremely simple hardware interfacing
Typically lower power requirements than I²C or SMBus due to less circuitry (including pull-ups)
No arbitration or associated failure modes
Slaves use the master's clock, and don't need precision oscillators
Slaves don't need a unique address -- unlike I²C or GPIB or SCSI
Transceivers are not needed
Uses many fewer pins on IC packages, and wires in board layouts or connectors, than parallel interfaces
At most one "unique" bus signal per device (chip select); all others are shared
Slide 41:
Disadvantages
Requires more pins on IC packages than I²C, even in the "3-Wire" variant
No in-band addressing; out-of-band chip select signals are required on shared buses
No hardware flow control
No hardware slave acknowledgment (the master could be "talking" to nothing and not know it)
Supports only one master device
Without a formal standard, validating conformance is not possible
Only handles short distances compared to RS-232, RS-485, or CAN-bus