With regards to the increment/decrement, I was wondering about that too. Maybe you could use some sort of rotary encoder? I was thinking it was more likely to use a pulseout statement. MC probably threw that in there for the old school programmers who were more familiar with that style of digital pot.

UPDATE: I've discovered that these are not either 8 or 7 bit resolution. There are one of the other. MCP4x3x is the 7 bit. MCP4x5x is the 8 bit. So for 7 bit, after the address/mode command byte, you would enter 0 - 127 for the wiper position. You do not need to add the /7 to tell it is in 7 bit.