I used a SOTA/ET2 combo briefly back in the late 80s.
In hindsight the SOTA table was not really the best platform as the ET's high moving mass was enough to unsettle the SOTA's suspension during play and induce speed instabilities. But at the time there were no alternatives.
So avoid floppy spring suspensions.
It really needs a totally stable platform like a VPI HW-19.
It was nicely made and as long as it was installed properly, very easy to setup.
The large VTA guage made that adjustment a doodle.
Azimuth was trickier as there was almost no movement available.
Maintenance was minimal ...just keep the bearing tube clean,avoid any kinks in the airline etc.
I didn't have the setup long enough for any major problems to develop.
The real headaches come with the servo controlled arms like the Goldmund T3/T5s, full of wanky electronics just waiting to breakdown and drive their poor owner crazy.
Peformance of the ET at the time was nothing short of amazing.
Nice frequency extension at both ends, a huge soundstage and imaging that was very good but lacking the exceptional clarity and sharpness of a really good pivoted arm the old Alphason HR-100 or Syrinx PU-3.
Today given the choice of a tangential tracker or pivoted arm, I would probably take the simpler option and go for a pivoted arm on a non-suspended table. The best pivoted arms are more than the equal of any tangential arm.