The Index is awesome. Ive owned one since launch and have a lot of hours in it.
Super comfortable, large FOV and sweet spot, excellent colour, good resolution, class leading tracking, very good integrated audio and most importantly the option of multiple refresh rates - 80hz being perfect for sims.
On the down side the glare can be distracting at times but you get used to it. Its certainly nowhere near as obnoxious as the old god rays from the days of the Vive Pro and Rift CV1.
I also have a Reverb (owned since launch) that destroys everything on the resolution front and for certain experiences is in a league of its own (certainly for Elite its the best) but it is not without shortcomings. The colours are washed out, mura is visible in bright uniform scenes, the FOV and sweet spot are smaller than the Index.
Last in the bag are a Pimax 4K+ and a Rift S (both owned since launch) but i dont use them nowadays as they dont really cut the mustard compared to the Index and Reverb.
I use the Reverb for Elite and Assetto Corsa and i use the Index for American/Euro Truck Simulator and Assetto Corsa Competizione.
If you are coming from a Vive Pro (i owned a Gear VR lens modded Vive Pro as well so have experience with a decent OLED HMD) you will initially be a bit shocked making the transition to LCD as the blacks are not inky black - there is glow from the backlight that adds a perceivable haze to a dark low contrast scene.
In my experience its simply a matter of time before you adapt to it and dark environments feel properly dark. Other users experiences are at odds with this and some maintain that they never adapt and always find dark scenes to be no good in LCD HMDs. Its been a bone of contention since day one and you have to be prepared to deal with this when you make the switch to LCD.