There are different opinions about the Trap Bar, with the majority giving it a thumbs down because it doesn't carry over well to the regular deadlift. For people that don't compete in powerlifting, the Trap Bar is a great option. You can't argue the benefits of picking up something heavy off the ground whether it it be a Trap Bar or straight bar, so who am I to say it's not good? Also, if someone performs a Trap Bar Deadlift with 800lbs are they not strong?
The biggest advantage to the Trap Bar is the handles – they keep the bar close to your center of gravity. So in theory, it will make the lift safer. The Trap Bar also uses more quad than a normal deadlift. I've heard stories of people doing high pulls with a Trap Bar but I've never figured out how that worked. It's also great for doing shrugs and drag rows, but I wouldn't buy this bar just for those two exercises.
The Trap Bar is very easy to teach which makes it ideal for large groups of athletes/a single coach. Since the vast majority of strength coaches have limited/no help and are short on time, the trap bar is a welcome addition. Also, and this is only anecdotal evidence of about 200 subjects (not enough to be worshipped at the altar of EXERCISE SCIENCE*: which reminds me that I must flagellate and then fellate the Golden Statue of STRENGTH SCIENCE*), the trap bar deadlift can be trained much lighter than any other lift while still making progress/getting stronger. In other words, my athletes can use a very light Training Max on the Trap Bar; which ensures that they aren't burnt out for skill work, conditioning, speed training, agility AND other strength training. It's a win/win for a coach. Stronger athletes and fresher athletes. This is obviously a great thing for in-season training. Since we all know that being stronger during the actual competition is more important than the off-season, this makes a huge difference. We have also found that it is easier to recovery from a Trap Bar workout than a deadlift or squat workout. Again, this is common sense due to the hamstrings.
Also, please don't use the high handles unless you are injured or are unreasonably tall.
The one drawback to most Trap Bars (or Hex Bars as they're often called) is the short sleeves. Even with the thinnest of plates these sleeves make it very hard to get appreciable weight on the bar. I was lucky enough to purchase a larger Hex Bar about 10 years ago but can't recall where I bought it. If you're stronger than the average person this may prevent you from using this bar in any meaningful capacity.
*Note: Any words in all caps must be read with baritone and monotone effect or filter.