I used to to quickly look for sparkly. I usually do it while mining so I can quickly go to the next rock. I just started doing that because I actually forgot I had the skill for a while.
I use it all the time in the ancestral lands on a dead end street. I'll eyeball partway down, and usually all the toe traps are tripped and the quions are taken, so I leave. It's faster than hairballing there and back.
I also frequently use it mining (all the time really)
I thought it was a useless skill until I got it (it was quick!) and now I use Eyeballery all the time. What everyone said above, and I use it all the time to find shrines and resources on multi-level streets.
Overall, the usefulness depends on your play style, and I can't say it is worth getting early on, but it can be a time saver.
You can use it while auto-running, so I use it in the ancestral lands to see if I should bother ducking into any holes. I also sometimes use it to check key spawns if I know there are some in the area. It doesn't do much good in most mining areas where there is plenty to go around, but in Neva Neva or AB, it's faster/easier than jumping around in circles.
I am quite bad at navigating the streets with multiple levels that require jumping. Eyeballery is very useful to me to spot mining rocks, firefly swarms, jellisac, and other items that may be in hard to reach spots. It lets me know whether it is worth my time, frustration, spinach and levitation to try and get there or not, and helps me try to find easier routes.