I have recently converted to the 'indoor cats' way of thinking, and unfortunately it was heartbreak that made me realise that this is the way to go, for the safety of my kitties, for my own peace of mind, and for the wellbeing of birds etc. I lost my beloved boy Shaggy, 3 days after my 21st bday, to a car just outside my house. He'd always been an outdoorsy type cat, he used to get cabin fever when I kept him in for too long, but the devestation I felt when he passed was like nothing I'd felt before, I truly felt like I'd lost a part of me. He was almost 5yrs old, and was my baby.
Eventually there came a time when I felt ready to adopt another kitty (thought the pain still hasnt eased, I still hurt every day), he's now almost 6 months and has not been outside once since he has been in my care. My partner has suggested letting him out once he has been desexed, but I dont think I will be able to let that happen. We're moving soon from a coastal area to a suburb at the foot of a mountain, and of course I would worry about his own safety, but also him harming the innocent and beautiful native Australian birds. Hunting is a natural behaviour for cats, that is true, but I dont believe that makes it ok to unleash my cat onto them.. especially considering alot of them are protected species.
IMO, the best way to go is to build a safe run/play area in your backyard. These are quite popular in Australia, and while I've seen some dodgy ones, with careful thought and planning, I think they can be great for cats who would otherwise spend their lives inside.