Stan, a one-function device would work for many applications, I tend to look to see how broad a spectrum I can cover if the costs don't get out of hand. The other plus is that the uP can be reprogrammed if a new requirement comes along. However, there is merit to placing some sort of limit on the functionality to keep the cost and complexity within reason.
If this ends up being something the user builds, he could also leave off parts for extra channels if he doesn't need them in his application.
