An often asked question is why do you keep chickens. The answer is easy - because previously whilst on "gardening leave", we decided to create a vegetable plot, which in turn turned into "why don't we have chickens" (meat and veg !). On reflection, this was a really good decision, since they are a bit of fun and handy for disposing of un-wanted vegetable matter, bugs, snails, slugs, in fact anything that wriggles or looks like it might wriggle sometime soon. A Chickens view of food is "if it looks like it might be edible, then give it a try and take it from there" - as various frogs, sloe worms, worms, bugs and other unidentifiable food sources have found to their peril.
Secondly, chickens are good fun, they have individual characters and attitudes, ranging from the chatty ones to those that look down their beak at you with the "what ARE you doing human" type questions in their eyes.
There's also the eggs - lots and lots of fresh, golden eggs. Its amazing how different the are to shop eggs, hard shells, firm whites, golden yellow yolks, double yolk eggs. They are also good to trade with neighbors as everyone seems to prefer fresh eggs.
Conversely, on the negative side, there is chicken poo everywhere (which smells bad), they will eat anything they fancy - your prize garden plant - well its just looks like a couple of calories to a chicken.
If you like your garden, then realize that a patch of earth is an ideal place to have a dust bath's to get rid of all those parasites. It may look like your newly tended border with a new plant in it, but no, to a chicken, that's a bathroom with a free snack, including the various bugs that come out and get eaten during the cleaning process - Meat and two veg, chicken style. Similarly, that fresh grass you put down, to a chicken its a tender snack to chow on.
But, all in all, as long as you manage them with fences and "garden parole" then its a fair trade. They dispose of things you don't want or need and give you a bit of fun and fresh eggs. All you have to do is to do a bit of chicken husbandry, which may involve anything from a regular worming session through rescuing something that looked like food and got too close, trying to identify which of the 140 ish different problems a chicken can get.
My favorite quote from a local vet when we first had chickens, and weren't sure what to do resulted in the vet explaining in no uncertain terms that if you get livestock, then you also get deadstock and being able to decide when its the right time for chicken euthanasia (an the possibility of an unexpected curry) becomes a necessary skill.