Cardio has been getting a lot of bad press laTely. And with good reason it would seem. It shows that it is not all that good for burning fat as you stop burning calories as soon as you stop exercising. It can give you repetitive strain damage in your joints and for a lot of people it's just too boring!
But there are good sides to cardio which is often overlooked. Cardio is probably the best common exercise for improving the mind (well, other then yoga). You learn a far more determination jogging a 10K then you do from sprinting up hills. You learn a lot more about yourself, you have time to reflect and it's almost spiritual really.
Secondly, if you are a beginner to the world of health and fitness then cardio is a perfect starting point. You can start to build up a basic level of fitness and you will not feel sore the next day. Let's face it; a lot of workout programs are really hard work for some people, especially those who need them the most. Cardio is a very good way to easy such people in. In fact, some workouts would actually injure obese people so cardio is a very good way to go for them.
Thirdly, if you enjoy long distance running then you should stick to it, regardless of what anyone ever tells you. If you enjoy something then you are going to stick to in and it will be better for you in the long term. And there's nothing better then long term health.
To sum up, there is a lot of argument over the effectiveness of cardio. I would argue that it's a good way to ease in if you are a beginner and then you should start using a well designed program such as The Truth About Six Pack Abs. However, if you really enjoy cardio then you stick to it, you hear!