You're right, my experience with my own (plug-in) hybrid is that the manufacturer's claimed electric range of 32 miles could only be achieved on completely flat terrain at a constant 55 mph. If I'm very careful, I can (after 3 months' experience) get 25 miles, but in winter with heating, lights and wipers going, 20 miles would be a struggle (and battery performance is worse in cold weather).
The other problem for Tesla owners must be recharging. My car has a 10kWh battery and takes 5 hours to recharge from empty* using a standard domestic 3-pin socket** (2.3 kW). If you went for the fully loaded Tesla with a 90kWh battery, that's going to take almost two full days to charge at home. You can charge the Tesla (and my car) much more quickly at the high-power outlets now available at most motorway services (when they're working!) and increasingly in super-store car parks (or at your work if they have one), but for many people that may not be an option.
* Actually, the car's computer won't let the charge drop below 15%, partly to protect the battery (Li-Ions don't like to be totally depleted), partly so there's enough juice to start the petrol engine when necessary.
** I could (at non-trivial cost) get a dedicated 16A socket installed at home, but that only reduces the charging time to 3½ hours, which (for me anyway) isn't worth the money.