I leave it on or select mode 2 for motorsports. Rather annoyingly Ive accidentally switched IS off several times without knowing it while handling my 70-200 IS. This happened quite often on the MkI version of this lens and I need to monitor this behavior on the MkII. If it occurs again I will probably tape a small piece of toothpick in the gap next to the switch to keep it on.
5D3, 5D2, Sony α6000, S90 | SY14 f/2.8, Ʃ20 f/1.8, 24 f/2.8, 35 f/2, Ʃ35 f/1.4A, 50 f/1.8 I, Ʃ50 f/1.4 EX, 100L Macro, 17-40L, 24-105L, 70-200 f/2.8L IS II, 1.4x II, 70-300L, 100-400L | E-mount: SY12 f/2, Ʃ19 & 30 f/2.8 EX DN, 16-70 ZA OSS, 55-210 OSS, Metabones SB | FT-QL, AE-1P | FD(n) & FL lenses