I love caddies! and I am one myself. I spent this past summer looping at Quaker Ridge, and had the best summer of my life. I was the first one there, arrive at 6am to be the first on the sign in list, and the last one to leave every day. I quickly worked my way up and was one of the top caddies by the end of the summer.
At Quaker, members are required to take caddies until 3pm every day, although carts are allowed for those with medical reasons. Even when members were in carts, a fore-caddy was required because it speeds up play, but because caddies are relying on these loops as income... most of them paid full fee even when riding.
There is no way that having a caddy doesn't speed up the round. Normally we had 2 caddies in every group, one grabbing the pin and reading greens, while the other one drops off drivers at the next tee and goes off to fore-caddy. In general you would alternate who grabs the pine, but the key is to work as a team. Both caddies shouldn't be raking green-side bunkers, we would signal to each other, so one person grabs the pin, the other takes care of the bunkers, and then hurries ahead to the next fairway. In some cases, if one caddy isn't comfortable on greens, then he will go ahead all day.
Also, this summer (my first summer) the club started using the laser guns that give exact yardage to every pin. While I resisted at first, they absolutely speed up the game even more and are pretty accurate. I found they work best in combination with the markers, so i give the players a more accurate reading from the center of the green.
For the most part I found that the older guys, the career caddies, were the best, and most numerous at Quaker. Unfortunately I found that a lot of times, the player would be intimidated by them, having a man the same age or older carrying your bag in the hot sun can be a little odd, and thats understandable. Then there are kids, who sign up because they need money for school, and discover this great game, play with mixed sets the caddy master puts together for them, and are always begging to play. I found that these kids are often very good, but are often to shy to speak up even though they are probably better than their player. The guys who showed up to make a little extra cash on the weekends were hit or miss. But the kids who got the job because daddy knew a member of the club were the worst, they were oblivious to what was going on 90% of the time.
As I'm sure you have figured out, I absolutely loved caddying, and not just because of the pay, which was unbelievable. If I went home with less than $150 in my pocket I was unhappy. But there is just something about being out there, pulling clubs, reading greens, that I enjoy. After a summer on the job you have a better understanding of the "average golfer", and I recommend picking up a loop to every architect. Also there is not a doubt in my mind that having a caddy makes you a better player... but I probably wouldn't caddy for $20, and there would be no such thing as a career caddy for $20, how can you expect some of these guys to put food on the table for their kids at $20? If you want caddying to die, drop the fees to $20!