When I used to visit Florida years ago, even at the busiest of times there was no option other than queueing for the attractions. Depending on the time of year you visited, you could be lining up for anything up to 2 hours to ride a 90 second ride.
Both Disney and Universal have tried to combat this problem with a “speedy pass” concept. However, they are operated in very different ways.
Disney’s FastPass
With the Disney system, each attraction that is part of the FastPass system has 3 different areas near the entrance to the attraction. There is the regular “stand-by” line, the FastPass line and the FastPass distribution area. To use the system, you make your way to the attraction’s FastPass distribution area, put your park ticket into one of the machines and it gives you a ticket with a printed time range on it. Then you simply return to the ride some time in the range on your printed ticket and enter the FastPass line. You will generally be able to ride the ride within 5 or 10 minutes. You can only hold one FastPass at a time. You cannot get a new FastPass until the start time of the one you currently hold has passed.
WDWInfo.com has more information on FastPass, including a list of attractions that are currently using the system.
Universal’s Express Plus Pass
Universal charge for their Express Plus pass – $35 per person for a single park, $50 for both parks (and it is the same price for adults and children alike). This is on top of the cost of a regular park ticket. This pass lets you ride every Express Plus pass attraction once and once only, and they guarantee a wait time of less than 15 minutes at each.
More details on the Express Plus Pass can be found at the Universal website.
Comparison
The Disney system is OK – for the most part it works. It has a few drawbacks though. First, you need to visit the actual attraction to get the FastPass tickets. This means you potentially have to trek to a completely different part of the park, just to pick up a ticket that might not be valid for a while. The biggest issue is the way in which FastPass tickets are distributed. When the park opens, the time window is 9am until 10am. As people begin getting tickets, and the quota of FastPass tickets for the current time window is met, the time window advances forward to 9.05–10.05. It then moves in 5 minute increments as more and more people show up. This is fine for most rides, but for very popular rides this could be a problem. Today, we went to ride Expedition Everest at Animal Kingdom – we arrived at the ride at 9.20am (20 minutes after park opening) and the line for the ride was already 70 minutes, and the current FastPass window was 12.55pm to 1.55pm – almost 3.5 hours later.
When I first found out the cost of the Universal pass, I was pretty horrified. For a family of four, this amounted to a cost of $140 plus tax, and that was on top of the price I had already paid for the entrance tickets. When we toured the original Universal Studios park, the crowds were not too bad, and we just bypassed a couple of the rides that had longer wait times. However, when we went to Islands of Adventure, within about 45 minutes of park opening most rides were at least a 45 minute wait, a lot of them over an hour. It was a really hot day, and the kids were already starting to moan, so I relented and purchased the tickets I had previously written off as a rip-off. We then proceeded around the park, entering each ride and riding within an average of 10 minutes. Almost every ride is Express Plus enabled. It made touring the park a complete joy, and I felt kind of sorry for the people lining up for well over an hour to ride the amazing roller coasters etc. The main drawback with this system was hearing “cool! can we ride again Daddy, please!” as soon as a ride was over (since the ticket is good for one ride only on each attraction).
Universal’s system is very expensive (IMHO), but an excellent way of touring with smaller kids and hitting every single ride. Universal limit the available tickets for any given day, which guarantees the 15–minute maximum wait time. I give it 4 out of 5 (with the cost disallowing a 5 out of 5 rating). 
Disney’s system works, as you can always find things with short lines to fill the gap between FastPass attractions. The Expedition Everest example seems to be an extreme case. However it can cause a lot of extra walking and requires extra planning to decide which order to get your FastPasses in. I give it a 3.5 out of 5. 
So, neither are perfect. I wonder if there is a hybrid that is possible. Maybe Disney could allow you to hold a couple of FastPasses at once. Or maybe they could allow you to get a FastPass for any ride in the park from every single FastPass station (hence cutting down on the walking aspect). Perhaps Universal could allow you to get priority access to 3 or 4 rides for free, before making the expensive charge.
Whichever system you prefer, it is better than the system that was in place when I last visited in 1996 – the “wait in line regardless” system.