Depth perception is an issue.
The red spot on the ground is a work-around, as is the red line to the ground in neXt. I have not seen or used any of the 3D glasses on a monitor. Some are red/green (anaglyph), some are (active) timed shutters, others (circular) polarized light. Perhaps they are awful and annoying I do not know. Is it worth considering? Flying with one eye closed is not so much fun.