There are plenty of catches, including a requirement that anyone using Google Balloon Internet would need a receiver plugged into their computer in order to receive the signal. Google is not talking costs at this point, although they're striving to make both the balloons and receivers as inexpensive as possible, dramatically less than laying cables.
The signals travel in the unlicensed spectrum, which means Google doesn't have to go through the onerous regulatory processes required for Internet providers using wireless communications networks or satellites. In New Zealand, the company worked with the Civil Aviation Authority on the trial. Google chose the country in part because of its remoteness. Cassidy said in the next phase of the trial they hope to get up to 300 balloons forming a ring on the 40th parallel south from New Zealand through Australia, Chile, Uruguay, Paraguay and Argentina.