If you use a USB keyboard with the laptop the laptop can be moved out of the way. Then your laptop is just used as the core computer, like your PC tower. Personally, I prefer the PC even though I also have laptops, but a laptop makes a good substitute for the PC tower, especially if you have a laptop dock, which makes connecting and disconnecting the laptop very easy.
Cloud computing is changing the definition of personal computer from a fixed location to everywhere you go. A classic case to describe such a change is where to save your cash, in your mattress or a bank account. The change is irreversible, isn't it? Cloud is not perfectly safe place, so does your personal computer. Cloud computing saves maintenance and upgrade of hardware. Cloud computing is where the network is well maintained and administered. Virus is often found and identified from a PC on the network. The less PC, the safer network and more productive. See, you can't win this debate.
So how effective is the cloud when you're network connection is down? No organization is immune to data theft or data loss. Some of the worst security breaches happened to the FBI, RSA, and other organizations that specialize in cyber security. Some clouds may be OK for offsite backup but it's a very risky scenario to depend any remote operator for critical data.