Only good for 500 miles and not for everything. Does not cover, for free anyway, running out of electricity or iirc, flat tires. It's intended for parts or system failures - things explicitly covered under warranty. At least as written. Now, if a tire came apart due to a defect, then I would expect that to be covered at least if the tires were bought from Tesla.
And beware AAA - a disreputable dispatcher kept me waiting an extra 3 hours in the cold and then extorted $95 cash by calling a tow truck that was not based where I was headed. You see, if you read the fine print, tows back to the point of origin (towyard) are done at no extra charge. Yep. So they started with the right truck, and then changed midstream. How do I know this? The second towing company owner told me. At 4am they had kept him waiting as well, and he wasn't happy. Fortunately the tow truck himself did his absolute best - still incurred a few hundred dollars damage to the car, but that was the result of a judgement call on my part, so that's on me. Needed a half inch more clearance and we just didn't have it.
Anyway, don't run out of electricity and don't have a flat and you should be fine. Most of the places without an SvC within 500 miles do have Rangers. Except on weekends when they are not available. Not that I had to drive 1800 miles without cruise control of any kind to get to an SvC or anything. On a weekend. Phenomenal service from that SvC when I got there though. Best service from any auto facility ever.
Added: Just saw David's post - absolutely that kind of support is also stellar. I got to an SC that was dead one time; turns out the entire town had been without power for 3 hours and the ETA was "we don't know". Tesla had a flatbed to me in 25 minutes and would have towed me to the next SC. Fortunately just before we were to hoist the car, the power came back on - it wasn't great, but it was enough to get me to the next SC, and finally returned to normal the next day.
lol 
