I have mixed feelings about the inclusion of non-Teslas being able to charge at Tesla Superchargers, though if Tesla likes it I'm inclined to favor it.
The Bad:
For one, are hybrids with a tiny battery going to try to charge there? Will these cars have to shut off their gas engines to charge I presume? Hopefully no hybrids allowed.
There's a certain elan to the Supercharger experience being 'all Tesla'. I love this. Seeing a bunch of random EVs won't be as cool....or will it be better? I love the Tesla-only vibe right now.
Congestion is a thing in certain EV-heavy hotspots such as California high-traffic Superchargers during holidays. This is already an issue now.
Non-uniform charging points on non-Teslas. Right now things are organized with an all-Tesla charging party. A lot of cars won't have trouble accessing their charging port, but I can see LEAF owners sticking their rear ends out too much so they have room to get the charger to the nose port. Others may be tempted to take more than one stall in a pinch, which Tesla have said they will explicitly warn against. This could cause conflict if some obstinate non-Tesla owner decides to test this in full view of Tesla owners.
Another potentially chaotic situation is that someone with a charge port on the right side of a vehicle may use a neighboring stall (to the right) to charge. This is effectively taking two stalls, which Tesla will explicitly warn against. Non-Tesla owners have to input their stall number, but if they lie and say they're in stall 2 (to their right) and are parked in stall 1 then they could game the system and still take two stalls. Tesla owners aren't going to be happy about this, and it wouldn't be intended usage per Tesla. Hopefully they have a way to prevent gamesmanship.
People can buy non-Teslas with far less of a penalty now because they still get to use Tesla Superchargers. Tesla does not have a demand problem but this network being Tesla-only was a perk for Tesla owners and a reason to buy a Tesla. Having owned a LEAF formerly, that network was pathetic....if one can call it a network. This really is a factor for some, but there are good sides to non-Tesla owners being in close proximity to Teslas as well (below).
Some non-Tesla owners will be haters despite using the network. This won't be good for area upkeep, vandalism, litter, etc.
The Good:
Tesla's mission is to "accelerate the world toward sustainable energy" and this dovetails perfectly.
As others have noted, non-Teslas will pay more, will have to note the stall they're in, won't have full app privileges, and will have proximity to Teslas and their owners. This will cause some people to just move to a Tesla. Being around an ingroup can make one want to join that ingroup.
Reduction in hostility between marques. Hey if someone is relying on the Tesla Supercharger network, they're going to build some affinity for Tesla if they didn't start out that way. It's a huge favor to non-Tesla marques. This assumes non-Tesla owners play nicely and don't block stalls due to their charge ports being on the 'wrong' side of the car. This may affect how future EVs are designed. Who's gonna put a port on the right side of a vehicle now if they can design a new EV that they know will be able to use a Tesla Supercharger?
More revenue for Tesla, though I understand that this isn't intended to be a revenue generator so much as a means to an end (charging on the go).
This is another way to reduce the incidence of ICE vehicles. Someone who really wants a non-Tesla EV now has far less range anxiety overall, especially for long trips. Net benefit relating to Tesla's stated mission.
Eventual standardization of charging, all run and controlled by Tesla. I think other marques (not just owners) should have to pay for this much like EV tax credits because this is a huge benefit to them. I do think charging does eventually need to standardize, and it could be Tesla's goal to BE that standard. That I support, and the incidence of charging stations will obviously go up in the future. It's still early days yet.