I've owned an ET2.5 for almost 25 years, mounted on a VPI TNT 4. With all due respect to @mijostyn , he doesn't know what he's talking about with respect to the ET arms. I would not consider mounting one on a table with a loosely sprung suspension, but on a stable suspension, the arm has few peers. I've owned an SME V and a Graham 2.2. Neither of them came close to a properly set up ET2.5. I still use the ET 2.5 and the Graham and SME are long gone.
Yes, the table needs to be dead level, and the arm tube and number of springs used on the counterweight assembly needs to be set up properly for the mass and compliance of the cartridge. Also the air pressure fed to the arm makes an audible difference. I feed mine with a shop compressor and adjust the pressure using a precision low pressure regulator. I realize this sounds a bit complicated, but once set up, I don't need to do anything but play records for a long time, it keeps the adjustments perfectly. When you get the setup right, it's pure magic.
Another big advantage is VTA on the fly, and due to an ingenious design, the stylus overhang does not change as you adjust VTA. There may be other arms that can do this, but I'm not aware of any,