OTOH, it takes nothing to sign up for the rental company's 'frequent renter' programs and that usually gets you access to a priority counter or line, which can save a lot of time when the regular counter is busy. Usually a car will be waiting for you when you get there, but depends on the facility and the busyness factor.
Yes, I've done that with most of the major rental companies, and I agree it does cut down on wait time considerably. My experience has been that the service itself still varies considerably by location (although I've still found it to be better when traveling on business). The vast majority of my rentals have been at airports and it's very hard to predict which ones will have better service; I've had very bad experiences at large airports where you would think they would have the process down pat, and good experiences at smaller airports.
There is one way to avoid this, at least in my experience: be a business traveler. I've noticed a big difference in speed of service when traveling for business vs. traveling for personal reasons. I suspect that rental car companies know that business reservations are (a) much more reliable in terms of the person actually showing up for the car, and (b) much less likely to be able to change from the specific car type that's been reserved, since that's being determined by some corporation's booking rules rather than an individual's preferences.