We have kept them for about 5-6 years now.
There are ways round much of it but a lot depends on the individual set up and sheer dumb luck.
Ours used to free range until a fox took three of them at 9am leaving only one. I shut her in the shed and built a walk in run, and then we got another five, but it was never the same without their being able to explore and hide behind trees and rustle about under the hedge.
We weren't in the garden enough to make free ranging viable.
We now live elsewhere with a smaller garden and only one chicken left and she is out and about all day - I figure if a fox does eventually turn up, it will at least be a quick way to go.
You do have to let them out very early, unless you have a shed with run attached (we built the run onto the side with a high up pop hole and a ladder) and then they can let themselves in and out
We did get rats - unless you pave under the entire run, you probably will.
Never leave food out overnight - put their grains and pellets out first thing then hopefully most will be gone by bedtime
They do put themselves to bed, handily, unlike rabbits...
The smell isn't something I've ever found a problem.
Main disadvantage for me is holiday care (though you can build a pretty good set up and they will just need feeding once a day/water checked) and also when they get ill, not knowing what to do - but most vets will have someone who understands chickens, and often they are kind of dead or alive, and not much in between iyswim.
Also mites and lice etc will want treating, we've been lucky and not had too much of that.
But they are generally a joy to have around.