I absolutely love Time Machine with Time Capsule! Time Machine by itself was cool enough when I was using it with an external drive on my desk. The only problem with that scenario is that everyone in our house had to have their own external drives for backup. I have a MacBook Pro, we have a Mac Mini sitting in the “server room” in the basement, and my wife and twin daughters each have their own Macbooks. So, as you can see, that would be a lot of external drives to buy/maintain.
Now with Time Capsule, I can point Time Machine to the drive inside there and all our machines get backed up automatically to one central point in the house. Since my wife doesn’t spend much time with her machine hooked up at our desk and since the twins are almost never at a desk at all, having a Time Capsule allows their machines to be backed up no matter where they are in the house.
I purchased the 1 TB Time Capsule and, even with all 5 machines backing up to it, we’ve used only about 160GB of space over the last 3 weeks or so of use (and of that, over 150GB of that was for the initial backup). At that rate, I expect us to be able to back all our machines up to the Time Capsule for many, many months.
Time Machine isn’t the “be-all, end-all” for backup though. For us, it’s one side of a two-pronged backup strategy. I also use Mozy’s off-site backup service to back up files nightly to a place outside the house. I once lost a TON of photos and business files because I didn’t understand the importance of backups. Because of that, I’ve decided that you can never really be “too backed-up”.