Pros: Fast growth, big meaty birds, pullets mature into reliable egg layers, GREAT cold tolerance
Cons: FLIP in cockerels, hens are short-lived due to heart problems, heat intolerant, and huge amounts of POOP!!!
We've been raising these birds for years. Aside from a tendency to heat intolerance, the biggest downside to this breed is the HUGE amount of poop they produce - think turds the size of golf balls, from every bird, all day long! Other than that, they are relatively trouble-free birds, as long as you don't overfeed them.
A little known side benefit of this breed are their eggs - I usually order all roosters and the few that turn out to be pullets get added to our laying flock. The pullets lay enormous eggs with huge yolks on an almost daily basis. They begin laying at about 20 weeks of age, provided they are hatched early enough in the spring to allow them to mature by late summer (pullets from late summer or autumn hatchings often never begin laying at all); unfortunately, most Cornish cross hens only live to about 18 months of age, due to a tendency toward heart problems.