I agree with JillyBeanz absolutely!
I'm not what I would call an experienced owner, but I have had a few experiences (make sense?)
Alfie has never been clipped. When we first brought her home, she was 12 weeks and flying within the week. The first thing I did was walk around with her on my hand and show her all the windows and mirrors, let her get close enough to them so she could touch them with her beak. we have 5 windows in the space where she lives. When she did start to fly around she never flew into the same window twice! These birds are very intelligent and can learn very quickly! I must stress that when she flew into the window, she did not hurt herself, maybe her pride a little! She was still very young and had not yet the skill or strength to fly fast and do damage.
When Alfie was around a year she chewed her left wing feathers so badly she lost the power of flight completely, she could crash to the ground somewhat gracefully, but couldn't get any lift. When she realised she was flightless, I can honestly say she became very quiet and withdrawn - almost depressed. Looking at it from a birds point of view it's a no brainer - these birds were born to fly.
There are some who free fly their birds, but personally speaking, I would never risk it! Even the most well trained bird who is absolutely bonded with their owner can get a fright out in the open - game over! Just ask anyone who has ever lost a bird through free flying if they would ever try it again.
Alfie has an Aviator Harness and enjoys coming out for walks with the dogs in the summer! And out in the open can have a good fly around. She also does a lot of flying in the house and it's just awesome to watch her!