I would say for the UK it seems to have distinct disadvantages in the long term. Chinese and Indian Corporates have far more potential to outgrow buy up and streamline smaller UK companies. When the only interest a company pays attention to is that of it's share holders then society has problems. Unfortunatley there are no real checks and balances, or any effective moderating legislation. It is a cliche but one fast becoming more true. The rich get richer and the poor will get poorer. We do not have a stakeholder economy just a shareholder economy.
Interms of growth and population size, I think wars often stimulate growth. With the worlds limited resources nature will limit us as much as any other species. War and starvation may be the inevitable outcome. That's if you believe this well respected scientist http://www.youtube.com/watch?v=mLA-Sn6bi-U .
Historians seem to think there is never any shift in global power without conflict. So the exchange of power from the US to China may not go smoothly. Especially with potential flash points such as Taiwan.
Then again, we might all use the great power for social cohesion called the internet and community group our way to a more peaceful and caring solution?