I use it a lot. Invaluable tool for scouting trails that are hours away. It's more or less useless when trying to look at obstacles and see if your Jeep could do them (need on the ground photos for that and even then things change). However, for mapping a route, it's second to none.
As an example...I was elk hunting this past year. There's a long story, but the part that's important for your question is that the last night we ended up hiking for over 6 hours in the dark, down a drainage we'd never been, that was incredibly difficult to hike. Steep sidewalls, thick brush in the creek bottom, no trail. Got back to the Jeep at 3am, exhausted and happy to be alive.
We had left some gear back in there, so I ended up going back the next weekend to recover it. Before going in, I used Google Earth to map out an alternate route in and out, using a horse trail I was able to spot on Google Earth. That weekend I was able to hike in, pack things up, and hike out, all in just over 4 hours due to being able to scout my path beforehand in Google Earth. Totally different experience.
So yes, in preparation, it's awesome. For in the moment type of stuff, used Gaia GPS. That app also saved my life that trip, but that's a story for another time.