If you're prepared to sacrifice space in your garden (and also some of your plants, and are not too fussy about a "neat" lawn!) then its great to keep back yard chickens - and you can always fence off your prized plants / veggie patch.
Ok, so they will dig up areas of ground and shred a tasty plant of its foliage in seconds, but they also earn their keep by providing fresh eggs on a daily basis and a plentiful supply of chicken manure which, when composted, produces a rich fertiliser (you don't knee "Miracle Gro" if you've got chickens!!)
Although chickens have only a small brain, they can be surprisingly bright and learn quickly (all part of the survival instinct). Their personalities can vary greatly, from aloof to wanting to be your best friend and following you everywhere.
Here's a useful link if you are interested in learning more about keeping chickens: http://club.omlet.co.uk/forum/
In the meantime, here are some favourite photos of some of my chickens, past and present: