@whart , go ahead and swing away whart. To start things off I do not have a problem with linear tracking. It would be the ideal way to do it. The problem is many of the designs cause more harm than good. Arms that are essentially pivoted arms that are jockeyed across the record on transports with modern controls could work fine. There is one German arm that does that and some older Japanese designs. It is an expensive stunt to do well as the mechanics have to be extremely precise and quiet. The German arm is some $200,000. The best current designs are the Schroder LT and the Reed 5T. The LT in particular is a brilliant design. Air bearing arms fail because of their extremely high horizonal masses and the rushing air tends to cause high frequency noise. They are extremely sensitive to level and tend to skate in one direction or the other depending on which way they are leaning. They are actually more sensitive leveling devices then the bubbles people use to level them. They are a very unfavorable platform for a cartridge. Yes, they work, but there is a strong tendency for reviewers and turntable engineers to avoid them for a reason. The amount of tracking error in a well designed and set up pivoted arm is inaudible. The cartridge is a very sensitive device. It is also a mechanical device that has to operate within certain limits to perform at it's best.
Your turn.