Well good job believing everything you read on the internet.
Rubber bushings, operating exactly as they said in that link, will add affect the suspension. They add both spring rate and damping into the equation. Which is nonlinear and hard to account for without complex models. They do not allow the spring/damper to properly do their job.
Poly is better than rubber in the fact that it is stiffer and will handle lateral and longitudinal accelerations better than rubber. The frction between the sleeve and the bushing can be reduced if you properly maintain them. This means greasing them and keeping them clean. If this is too much for people to handle, then maybe they should not modify their cars.
Also, the amount of friction isn't as high as you would think. Even if this friction coefficient is high at the bushing, they are operating on such a long moment arm, that the amount of frictional force at the wheel center, where it actually matters, is not as high.
Delrin is a good material for bushings that operate on a single axis. In places like sway bar mounts, it works very well. In control arms, it does not. This is due to all the problems that myself and Asterix and probably some other have brought up in this and other discussions. The control arms do not pivot around a constant axis, because of this, they would not load the delrin evenly. And because the delrin does not give at all, this would put bending loads into a suspension arm not designed for that type of loading. And in extreme cases it will fail. And in normal cases, it will fatigue the arm up to the point of failure. If you drive your car and drive your car hard with delrin bushings, you will have problems at some point. Even if stuff is not breaking yet, you are adding more negative effects due to the improper use.
The control arm failure was not due to material limitation, it was due to poor design. Yes, the arm could have been weakened just due to age and use, but the delrin accelerated that wear due to the way the arm became loaded.
Suspension component design is a whole compromise itself. Rubber bushings have their pros and cons, as do poly bushings and spherical bearings. If you're really building a high performance car, then spherical bearings would be the obvious choice. Their main downfall is more direct transmittal of road noise into the chassis. But they allow the movement and control of the suspension that you want with a high performance car.
