Ok, we all know how I feel about being able to extend life. Other than the fact that it would be completely boring to live that long...well, that's the only real drawback I guess.
The idea of this qusp seems like they turned the human (such as it is in the book) body into something of a computer, akin more to an Apple 2e than what we use now. My understanding is that these bodies can not function without a qusp, and the "user" can determine what kind of body he/she/it wants, much as a computer shopper can determine what kind of hardware is necessary to serve his or her purposes.
Ghost in the Shell anyone?
Bodies seem to be nothing more than computers that can run a program that acts as an intelligent being. Take the qusp out (or transmit yourself) and the body ceases functioning. Done with that planet? Recycle the body so another can be made. Nothing more than a useless box.
Here's a better question, and I may have missed it in the reading; What if the qusp was destroyed while it was occupied. What happens to that person? Sure, a local death may cause the loss of a few hours of "life", but what happens when the main essence of the person is destroyed? Could viruses affect it? What about EMP (assuming there is a way to create such a thing)? I would be more concerned about these things than living forever.