I started out with the Juiceman Juicer in 1997 and then got the Jack Lulaine juicer around 2002.
It's a lot of work, and a lot of noise, and often with quite a bit of waste, imo.
Also the expensive mesh screens usually don't last very long.
Some veg like spinach and wheat grass are not easily juiced. A masticating juicer apparently works better for that.
And, like anything else, you can over do it. You can juice too much. There are some people who take in too much carrot/celery/apple juice, for example because it's such an easy combo to process, and they end up getting a harmless orange tint to their skin. (ignore any political references).
And with most vitamins, when the body has it's fill it will simply eliminate any extras when defecating or urinating.
I've found if one simply eats nuts, seeds, broccoli, carrots, spinach, and the like along with fruits frequently, you'll get the nutrition your body needs. Whenever I have my labs done, there is rarely anything missing or out of normal range.
Juicing is really for burners or people who have temporary medical conditions that can be improved with certain juices. People who smoke, drink, do illicit drugs, do roids, consume coffee, soda, and eat some of the worst garbage there is...and then think they can make things all better with their health by taking in a concentrated amount of excess vitamins and minerals.
If you really want to clean out your innards, juice some beets. Its so potent it can stain the juicer red. You can feel the juice as it flows through your body.