Tombo, when you use a stacked dado set it tends to lift the workpiece which results in the rebate or groove that you're cutting being shallower than you want. To overcome this you have to keep constant downward pressure on the workpiece directly above the cutter, this is where a lot of the safety problems come from. At the very least use hefty push blocks, never ever feed the workpiece with bare hands, and you may well have to feed the workpiece through twice to get a consistent depth.
Personally I use a combination machine and it's easier to install the dado set rather than change the machine to use the spindle moulder, which is by far the better tool for the job (it gives a cleaner and more accurate cut), so for many jobs I will actually use a dado set, but on my machine I can swing the power feed over the dado set and feed the workpiece through with that. If I didn't have a power feed I'd be more inclined to look for another way to achieve the cut, such as a router or spindle moulder, and I'll only use it for cutting with the grain, it spelches badly on cross grain cuts..
I tend to think of a dado stack as being a bit dangerous and also a fairly crude tool that's more appropriate for joinery than cabinet making. You need to think about how you'll use the dado stack in order to overcome these two limitations, it's not a tool that gives safe, high quality results straight from the box.
