The value of an automatic sprinkler system is relative to the intensity of maintenance and aesthetics desired. If you already manually water your lawn regularly and you desire a moderate to highly manicured lawn, it could be worth it. Sprinkler systems save, time, money, aid in water conservation, and help achieve a lush, green lawn.
Saving time by not having to monitor and move sprinklers. No more rolling hoses or getting wet making the next move, an irrigation system requires very little attention once set up.
Over time, an automatic sprinkler system will pay for itself. The savings are incurred by eliminating overwatering, and providing perfect, efficient coverage. Hand watering is no match for the efficiency of an irrigation system.
Eliminating overwatering means no waste, no runoff and no more forgotten sprinklers or having to water the driveway just to get a patch of grass. A properly watered lawn is also healthier and less vulnerable to stress, pests or weed infestation. Reduced pesticide products are needed and can be watered in immediately for maximum effectiveness.
The most satisfying benefit of an automatic sprinkler system is the look of healthy, lush, green grass. Once the optimal times are dialed in the you won't even know the sprinklers are there. Remember though, lush, green grass needs to be cut more often and, if you live anywhere with freezing winters, the sprinkler system will need to be winterized in the fall.
As for installation, I strongly recommend hiring a reputable, professional, licensed irrigation contractor. It may look easy but it's not worth doing it wrong and, in some areas, it's required by law to have a licensed professional do the installation.