Linear Tracking Turntables - Best??

I would only go air bearing. Love the ET 2, would also go mg1 or trans fi terminator. You don't have to spend a fortune and they don't require constant fussing . I think when people say that they are not very mechanically inclined. 

The problem with air-bearing arms is that the lateral mass is often a multiple of the vertical mass. So you can be tracking at the right weight for the cartridge, but the lateral mass can cause visible left-right motion in the cantilever. When this happens, the tracking error is significantly higher than that of a radial tracking arm!!

The solution is a cartridge with a lower compliance. This might not work out all the well when it comes to simple tracking, as the vertical component (mechanical resonance) might not be satisfied. 

I used to run a heavily modified Rabco arm many years ago that got around these problems- but then had other problems, most notably mechanical resonance in the track in which the arm ran. I do think linear tracking is the way to go, but have yet to see an embodiment that solves all the engineering problems.

My Trans-Fi arm can taken away from me only over my dead body.

The much higher effective mass in the horizontal plane of most linear tracking arms might not necessarily be a disadvantage.  Bass is typically mastered monophonically, which means only lateral movement of the stylus tracing the groove.  The higher effective mass in the horizontal plane would keep the arm from moving so easily so that all of that bass information is imparted to moving the cantilever which means that all of the bass information is actually recovered by the cartridge.  This is the principle behind the Moerch anisotrophic tonearm.  I don't know if this is also what is behind the sound of certain linear arms, but, it might be the case.  With arms like the Walker and Mapenoll, I heard really deep and powerful bass.  

Of course the higher horizontal effective mass would be bad news with off-center records which could severely stress the cantilever.

Does anyone have experience with the Shroeder linear tracking arm?    

One cartridge that plays into atmasphere's point about the lateral versus vertical mass of air-bearing arms is the Decca/London's. The current Londons have a vertical compliance of 15 but a lateral of only 10, making them a good candidate for an a-b arm, at least in regards to effective mass/compliance.