There are two basic philosophies regarding these types of devices which can be descibed nicely by looking at the differences between Unix and Windows.
In the Unix world, people tend to like a large number of small programs. Each program focuses only on a single task. This lowers the overall complexity of the program and makes it easier to find and fix any bugs. You can also string together unique combinations of programs to generate an almost infinite number of possibilities. The tradeoff is that you sometimes have to string together a number of programs to get the results you want.
In the Windows world, people tend to like huge single applications that do almost everything. This increases the complexity of the programs, making it much harder to track down and find bugs. Of course at the same time, you've got this single unified app that does everything from make coffee to create world peace, and you're still limited to whatever features work reliably for you.
Personally, when I look at multi-function devices, I just ask myself, "What if something breaks?" I either end up buying a second device to replace lost functionality, or going without the other features while the one is being repaired. So I'm more of a Unix person you could say. One device, focusing on one function, and performing that function as well as posible. If you are willing to take that gamble, don't let me stop you. Combo devices can be cheaper and less mess cable wise than individual components. Just figure out what your course of action would be if any of the functions of the device stopped working.
We were looking to purchase a flat bed scanner to scan sheet music, but were wondering if we should go with the all in one scanner, copier and printer. (We already have a new printer that we just bought with our computer.) Anyone know the pros and cons of purchasing a scanner vs. an all-in-one? Thanks!