The only downside to the cast iron pots and pans is their weight and the difficulty of handling such weighty cooking pots and pans.
Plus, they do need to be taken care of. They shouldn't be cleaned in a dish washer, or some say with soap at all. After using, while they're warm, rinse them under very hot water and dry them thoroughly. Then a light rubdown with fat or oil will keep them rust-free. The best way to care for them is to use them - a lot. I've used them on the stove top, in the over and on the grill & smoker.
They are one of the best cooking tools because of their versatility. Get the pan hot on the stove top, sear your steaks (30-40 seconds a side), then pick up the pan and put it in the oven to finish (3-4 minutes a side). If you do burn something in one the pans, put the pan in the oven and set it to a very high temperature for about an hour (self-cleaning ovens work great for this). When it cools, all that's left will be fine ash. Dump it out and clean the pan, and you're back to new again.
I've read that they're healthy, especially for women, because they add iron to your diet. I've also read that the non-stick type of pans are not, because if you heat them too high, the non-stick coating starts to break down and adds things to your food that you don't want - e.g.: carcinogens.
If you take care of them, they'll take care of you!
(Agree with the Simplex - I have a #4 that boils water for my "porridge" every morning.)