I ride with two clubs both of which have weekend rides of 40-50 miles. One club has a more relaxed pace of 15-16 mph ave. The other club has faster rides, the B ride being 17-18 mph ave, and an a group that will have 19-20 mph ave. Pacelines form on both A and B groups of the faster club. One benefit to learning to ride in a paceline is several of the members of the faster club ride the California double centuries. We dont ride as fast on a double as on a weekend ride, but the benefits of sharing the pull for 200 miles are great. There are things you must learn about riding in a paceline for safety purposes, and a few that are courteous. For safety purposes there should not be sudden moves, such as stops or slowing down. When you are the 2nd or 3rd rider back you need to pay attention to the speed. You dont slow down or speed up, and if you cant hold the speed you need to drop to the back of the line. There are some exceptions, such as weaker riders who can stay with the line but cant pull at that speed. That being the case the slower riders take a very short pull then pull out to the back of the line.
As for the Bicycling poll, I enjoy all three: pacelines, group rides, and solo rides.