It takes about 5 seconds more than it takes to put down a trimmer and pick up an edger that's the same two steps away as your other attachment. Loosen nut. Pull out attachment. Put in new one. Wiggle it until it bottoms out. Tighten nut. It took twice as long to type this as it does to swap attachments, and I type as fast as I can talk.
For a long time, Stihl offered "gearbox" attachments. These go at the end of the shaft (loosen the torx screws and pull the trimmer head off for example), and that has an issue with dirt. The Kombi system is split in the middle of the shaft. Dirt really doesn't get that far up. And it is a tool-less change.
The only issue with dirt, is that when the attachment is separated, it can get dirt in there if you drag it in the dirt. You kind of just have to be a little mindful of that.
The difference in weight between the Kombi tool and the fixed version of the same is just the weight of the clamp, and that's well less than the weight of the gas in your tank. You really cannot feel the difference.