I just wrote a summary of some of my thoughts on the switch matrix on the LPC800, probably one of the best features of the chip and something I'll expect to see a lot more of in the future. Definately adds a lot of flexibility to tiny packages, though, since you're no longer dependent on the design decisions made by the manufacturer. I loved the LPC1102, for example, but no HW I2C made it a non-starter for me. I use I2C extensively. With the switch matrix on the LPC800 I don't have these problems anymore and don't need to resort to bit-banging digital interfaces (yuck!).
LPC800 Switch Matrix: Making life easier one pin at a time.