With apologies for posting several days after the last post, I think the biggest challenges for Tesla are competition from established car makers as they enter the EV market...
You compare to Nissan for experience, but the Roadster has been out longer than the Leaf. I believe Tesla has more experience and better technology. Nissan, BMW, etc., have more money to invest in R&D and marketing, but to date no-one except Tesla produces a car that goes more than 100 miles. The nearest competitor to Tesla goes less than 1/2 as far.
The other is batteries; their inherent limitations and public acceptance of them..... Even with fast charging,....it takes several hours to recharge a 300-mile car
No, fast charging charges at about 4-5 miles per minute when the pack is enough less than full. I've heard quotes of 30 minutes to add 150 miles to the 85kWh battery from Tesla and a total of 45 minutes to add over 200 miles. So, SF to LA is now possible with one 30 minute stop. That's maybe 10 minutes longer than a normal bathroom break/gas stop for me.
This could change with an all-day car capable of recharging overnight. But that's not a trivial matter. Assuming 300 Wh/mile, ten hours driving at 65 mph would need a 195 kWh pack.
EVs don't need to go 10 hours of continuous freeway driving to be successful. I haven't done a 600 mile drive in a day - ever - in my life. Very few people do that, and even fewer would do two days back to back like that. Once an EV does 500 miles, the quick charge thing becomes moot - you drive to your destination and then charge for a couple days while you visit.
Finally, it is too early to know how long the batteries will last.
Tesla warranties Model S batteries for 8 years, for at least 100K miles (unlimited miles on the 85 kWh). Is there any ICE car being sold today that warrants their drivetrain for 8 years/unlimited miles? No.
The real issue here is battery replacement costs and public perception of how long the batteries will last, not how long they actually last.
Competition, unknown battery longevity, battery cost, and public acceptance of the inconvenience of charging batteries on road trips.
The competition is worse than Tesla in terms of battery cost and range, and show no signs of surpassing Tesla. The issue of battery cost is getting better and better, and gas is going up in price. Charging on road trips goes away as batteries hold more juice (we've had a double in the capacity of the 18650 cells Tesla uses between 2004 and today), and 30 minute quick charging for the occasional really long trip will be fine for almost all.
You think the real challenges for Tesla are the challenges for EV acceptance, and then throw in that other companies will be better than Tesla. Well, if EVs can beat ICE cars, then the competition doesn't matter. Yours are all long-term challenges. The real issues for Tesla are short and medium term. Can they deliver Model S in quantity and quality on schedule? Are there enough people wanting to buy them at a 20K/year after 30K have been sold (And that's not an EV thing as much as it is a $75K car market thing). Can they make a Gen-3 for $30K and enough range? Medium term, will people start to realize the long term cost benefits of EVs despite their higher cost? (It's like of like solar in that regard, and Americans have a tough time seeing that, which is why they have the "solar lease" thing).