"With the consideration of using three of the bus lines for address output and for data input this total pin complement becomes 12 pins."

Yes thats correct.

But one can reduce a few pins :

Data : 8
Start+ALE : 1
Address : 3

( This setup will have to use a fixed delay for conversion instead of the EOC output )

The above will be the minimum if one wants to read 8 channels. And if anything less, maybe all three address lines need not be used. And in a memory mapped set up the 8 data lines anyway have to be there. So the actual number of dedicated pins of MCU can come down further.

Agreed, when compared to a serial ADC, the ADC0808 is nowhere near, irrespective of what setup one uses.

Raghu