I think this setup involving a TC to make things faster/smoother on the LOCAL NETWORK ONLY is genius.
If I want to play some music or movies via iCloud that I have stored in my home folder, I could stream them right off my own network so its faster and doesn't eat up my bandwidth cap.
But everything still needs to be really in the cloud too. What if I am a traveling sales person and my router at home shuts off for some reason, the HD fails, or another problem arises. I still need access to my files.
Plus, I bet Apple's servers will have much better upload speeds than my connection, so accessing "iCloud" on the go is going to be terrible unless I am getting the files off of Apple's servers.
And what if someone breaks into my house and steals my TC or there's a fire and it's destroyed. I have just lost all my files. That means I would need another backup solution. For me, the whole point of a cloud solution is so that I don't need to worry about losing my files again, which again the TC-only setup would fail at.
Now if iCloud is smart enough to figure out when I am at home and thus use my local storage (TC) or if I am outside and therefore use Apple's own servers, and it can do so seamlessly, now that's an improvement over DropBox and any other Cloud service.
At that point, Synching is not going to be an issue at home at all, since local speeds are super fast. And by the time I hit the road, I am sure that TC would have uploaded all the files in the background by then to the real iCloud.
So if this whole TC thing is that if you have a new one, it will make iCloud EVEN BETTER, then it's GENIUS.
If this whole TC thing IS the iCloud and you must have it on to share your files at all times, then its an EPIC FAIL.