> So... is this stuff really worth it?
I think it would depend on the person, which kind of paint protection was used. IIRC, there's two main types of paint protection, one is a PPF (Paint protection film), the other being a type of coating applied to the paint.
> What’s it tend to cost?
Perhaps others can chime in on the coating as I've not opted for that, but can speak about my experience with PPF.
The materials more or less will cost the same, what will greatly vary is the cost for labor. If you're looking for going the PPF route rather than the coating, I would recommend not to go with the cheapest solution (you usually get what you pay for), and look around for recommendations from others who have gotten PPF with a good experience. If you're local to the Bay Area, I've had good experiences with Mr. Tint and Invisiguard Clear Bra. Between the two, Mr. Tint is more expensive (although they have more locations in the Bay), and I prefer Invisiguard Clear Bra in San Carlos.
Cost-wise, here's what I 've seen:
Partial Front end: (front bumper, partial fenders, partial hood, mirrors) will range around $750 - 1k. When I bought a Forster a few years back, I thought this was good enough, but in hindsight, while the covered parts were well protected, I got lots of paint chips from the upper hood and A pillars which weren't and now wished I would have gotten the full front and sides covered.
Full Front end (front bumper, front fenders, entire hood, mirrors and partial A pillar) will range around 1k - 1.5k, which will be good for long-distance driving, or driving around roads with lots of gravel.
Full car (Entire car: A-Pillars, mirrors, front and rear bumpers, hood, fenders, doors, quarter panels, rear hatch): Ranges around $3.75k to 5k depending on material. I think this was a bit overkill, as there's parts that probably don't really need protection, like the rear hatch. Many folks get this option if they're interested in getting a matte look on their car, want 100% protection, and/or just have lots of money hanging around.
I've opted for Full front end, plus additional panels to protect, like the doors, rear bumper, and quarter panels. This cost a good chunk less than the full car wrap and IMO protected most of the important panels that are most susceptible to others opening doors on, rubbing up against (while walking past), or airborne rocks/gravel.
> Is it going to save me from that gravel truck up the road that has no overhead tarp on?
Having something is better than having nothing IMO. Although an important question to ask is-- How long do I plan on keeping the car? If you are leasing, or plan on selling the car in 2 - 3 years, paying for (full frontal or full car) PPF may not be a worthwhile investment. However if you plan on keeping it longer, or drive where there's lots of gravel, then that will help aid with preventing rock chips and slightly lowering the depreciation of your car at time of sale/trade-in.
> Will it save me from the teenager that decides that anyone with a Tesla must be “the man” and he’s going to get even with his keys?
That depends on the driver and where they park. I'm a bit more particular of where I park my car, and opt to park farther away in shopping malls as lots of folks prefer to park closest to where they need to go. IMO, this will help lower the changes of getting my car keyed. (NOTE: Here's where getting PPF on the doors, quarter panels and fenders will help).
> Is it mostly a vanity thing for me to get geeky over?
That's certainly one perspective. I can offer another-- If you've paid close to 100k (or whatever the purchase price was), I'd imagine that you also would like to keep the value of the car high, whether it's for resale, or otherwise. Getting PPF or other paint protection I think helps to add a level of protection your hard-earned purchase and isn't particularly a vanity thing.
If I was in the market for a CPO (or 2nd-hand) Tesla, I'd prefer for one that had PPF vs. one that did not or had lots of paint touch ups or was resprayed.
Hope this helps!