Swimming is a great exercise for your health. It's a full-body workout that combines aerobic and anaerobic training. Other benefits include zero impact on the joints and weight-resisted cardio.
In terms of other points, it depends what your goals are. Studies show that swimming is bad if you're trying to lose weight. Why? Despite the fact that you burn a lot of calories, people who swim tend to feel hungrier and consume more food after workouts rather than those who run or cycle (those two in particular actually make you less hungry). Swimming is also done in a chilled environment, meaning your after burn does not last very long since your body doesn't need to use as much energy to cool down once you get out of the pool. Also, swimming tends to exhaust most people; once they finish their workouts, they tend to fall asleep and not be active for the rest of the day.
Swimmers are known for having higher body fat percentages than other athletes. It's not that you can't be a lean swimmer, but if you look at people like Michael Phelps, who has a great body, you can see he's not nearly as defined as say a sprinter or diver.
So depends on what you want. I swim a mile a day and can't really imagine not swimming, but I don't swim to maintain a body shape, but rather I enjoy it. If you're looking to get lean, you're better off with other forms of cardio, but if you want to have a great overall exercise or do something in addition to other cardio, then swimming is a good choice.