What will it do for you? Buy this piece of equipment if you want to strengthen your upper body and stomach muscles. More specifically, you will be able to work your biceps (front of arms), triceps (back of arms), latissimus dorsi (the back muscle that give you that V-shape), pectorals (chest muscles), and abdominals (stomach muscles). Note I would not expect this piece of equipment to work any of your leg muscles if used conventionally. Of course there's a lot of accessory muscles that might get a little work-out too, such as your forearm muscles because you're gripping a lot, and parts of your shoulder, but the major muscles that will get worked the most are listed above.
How do you use it? You do a lot of the exercises hanging. Therefore, if you're not into hanging on to things, skip this piece of equipment entirely. The first big exercise you can do on it is the chin-up, where you're pulling yourself up to the bar and then lowering. This will work you biceps and lats the most.
You can vary the grip. Know that using a palms up grip is best, simply because you'll be putting your biceps in the most mechanically efficient position for them to contract, and so you'll able to pull up more times than if you used a palms-down grip. Try it- you won't be able to do as many chins with your palms down, or in a middle position. In fact, the palms down grip will work your biceps a lot less, so if you want bigger biceps, use a palms up grip! Switch grips for variety if you want- I'm just sayin' what's more productive and what works what the best.
The next big exercise is the dip. The dip will work your triceps and your chest muscles the most. Your front deltoid will get a fair workout as well. However, because the exercise is called a "dip", and setting this thing on the floor to do dips doesn't allow you to "dip" down very far, don't expect to get much of a workout doing a dip with the Iron Gym.
Next is the push up. You put the bar on the floor and do push-ups with it- which will work the triceps, as well as the chest. This is a good, productive exercise, and the Iron Gym makes it harder than a regular floor push-up because you are up off the floor and can lower yourself lower- which gives your chest a good stretch as well as making the push-ups harder.
Lastly is the sit-ups. You can put this bar on the floor to anchor your feet to help stabilize your body better to do a sit-up. Contrary to popular belief, if you are doing a sit-up with maximal effort (doing them until you can't do another one), EMG studies have shown that your ENTIRE ab muscle is contracting. Sooo, know that you're not working the "upper abs" more than the "lower abs" when using this device to do a sit-up- rather your whole abdominal rectus muscle is getting worked and stronger.
Okay, so that's the major exercises you can do, although I guess you could pick it up and make up a few of you own moves if you wanted to. A few details. Some people have had trouble with this thing fitting in their doorway. My advice is to just try it- if it doesn't work, ship it back to Amazon for a refund and call it a day. If you're an engineer, look at some of the other reviews that have given precise dimensions, get out your protractor, and measure away to be sure it will work. That's just too much work for me...
Will this get you stronger? Yep- but only so much. Anyone reading the strength training research knows that once you can do more than around 20 reps in a row, you're going to be building muscle ENDURANCE more than muscle STRENGTH. That's the major beef I have with these kinds of pieces of exercise equipment- there's no way to easily make the exercise harder as you get stronger. And if you can't make the exercise progressively harder, the muscle isn't stimulated to get bigger and stronger as time goes on- unlike exercise machines with a weight stack that enable you to gradually increase the weight to constantly challenge the muscle. Trust me, the guy in the video didn't get arms like that by just doing chin after chin using just his own body weight. Perhaps he had a small child grab his legs as he did the chins, or had his girlfriend sit on his back as he did pushups...
Overall this is not a bad piece of equipment, you just have to know its limitations- like how strong it will get you, and what muscles it works. A few tips. If you can't pull yourself up and do a single chin-up (have your wife or girlfriend try one for fun), just use a chair to stand on to get you to the top position, and then slowly lower yourself to the floor while hanging on to the bar- then repeat until you can't do any more. You'll find that after a week or two of doing chins like this (just the lowering part), you'll soon be able to do a full regular chin-up where you pull yourself up to the top position no problem. This works because you're about 50% stronger lowering something than you are lifting it. And for those who have a shoulder problem (or want to avoid one)- I suggest the rotator cuff exercises outlined in Treat Your Own Rotator Cuff