*Note: The ratings are based on my own personal experience over my term in Australia, not necessarily Global itself.
I owe a lot to the Global Work & Travel Co. I was lucky enough to win one of Go Overseas contests, and Global helped pay my way to Australia. It was a spur of the moment decision to go, and I am forever grateful for the opportunity I had. Living and working overseas was the best thing to happen to me for my own personal development. I don't regret it for a second.
That being said, Global itself is a mixed bag. Yes, they offer you guaranteed placement, but read the fine print. What I noticed talking to other Global travelers was that it appeared the company had no real "connections" and sent travelers' resumes to a handful of people that they found on the Australian backpacker board, Gumtree. They also require you stay somewhere for four months or they stop helping you. I had very little contact with them during my trip. I was frustrated when they sent me a job and I flew up from Adelaide in SA to Brisbane for a job that they hadn't told me I couldn't do without a driver's license. It was not entirely Global's fault, but they weren't particularly good at helping me find jobs I was after. I had at that time worked multiple years at home doing orchard picking so I expected to get jobs similar to that. Instead, multiple times they sent me to work at a bar, something I had zero experience doing and I had specifically said I was not really interested in. I liked the one bar well enough, but it is a tossup. I had one that was pretty bad, too. I was not the only one who had issues with there process and spoke with a number of travelers with similar problems.
There was also the contest issues. Yes, they paid for some of my travel. But they took me possibly the longest way to get to Australia in the first place (over the North Pole and through China) at twice the cost it would have taken to fly more direct. Instead of getting both my flights there and back mostly covered, my money was used up on the single trip out. I tried to send them a flight I wanted (I had gone back and forth to NZ before already and was familiar with the airlines), but they said I wouldn't get the money if I did it myself. By the time they got around to booking my flight, I was so close to my target departure date I had no choice but to accept their route.
Global can offer you a lot of help with getting oriented if you are new to travel. Most companies can offer similar opportunities and benefits. I went on their most expensive option and got set up with a debit card, bank account, phone, etc. But having traveled on my own before, I think it was unnecessary because there was nothing they offered that I could not accomplish myself.
My verdict: if you're new to travel, Global may offer some peace of mind. If you have traveled around before and feel comfortable with going through the process on your own, definitely don't waste your money. It's an expensive service that may not pay off. Australia is a country full of backpackers. Talk to them if you have problems and they might be able to give you tips to work it all out.