I didn't read through the thread, seeing as I'm not a patient person
But just adding my story.
I live in a town, nearly classed a city because of it's size. I live on a very busy road that will have at least 1 road kill a month (I know this doesn't sound like a lot, but that's because everyone here keeps their animals in). We have 2 indoor cats. We got them out of the neighbours garden when they were 3 weeks old, they were underfed and in very poor condition. Their mum was a victim of roadkill in our street, 3 days before we found the kittens. Needless to say, this already made us not feel too good about letting them out.
On top of that, a couple of houses from our, lives a guy who keeps pigeons. Rather than keeping his pigeons in, he kills cats that enter his property. Even if our cats would be clever enough to not cross the road when there's cars coming, I doubt they'd see the difference between their garden and ours. It's just a risk not worth taking here.
I'd love my cats to be indoors/outdoors cats, but it's simply not do-able here. We try all we can though, when it's nice weather and we're sitting outside we'll open the door and just let them out. They don't often leave the garden, they'll just chase the birds in our garden (they don't catch them, they're too loud and unexperienced
), eat the plants and strech and lay down in the sun. Though, when being kept inside, I can't say they're easily bored either. They're about 8 years old now, and run around the house like a puppy would.