I fell into the same trap. The MCP3204 and MCP3208 are identical. I've been told the new MCP3201 is identical to the 3204/8.
The MCP3202, however, is different. I don't remember the details, but I do remember it biting me in the butt.
Here is some working code that talks to an MCP3202:
http://www.eng.uah.edu/~jdw/avr/ttpv.pde
http://www.eng.uah.edu/~jdw/avr/radioshield_rocket_tracker.pde
-j