Honestly to me the worst thing about the new MacBook Pro isn't that there are no legacy ports on it or that the battery may be smaller, it's that the new all-things-for-all-people ports it has are confusing.
The ports are all Thunderbolt 3 ports, which I believe by definition means they are USB 3.1 ports as well. But some devices out in the world have USB-C ports that are not Thunderbolt 3 compatible. No longer can you tell what sort of devices will work with a port by its physical shape. For instance, I have a Windows desktop machine with a single USB-C port on the back, but it's not a Thunderbolt 3 port. So while I could physically plug in a Thunderbolt 3-only device, it wouldn't function at all.
Thunderbolt 3 is backward compatible with Thunderbolt 1/2 via an adapter, but the Thunderbolt 2 adapter that Apple sells does not function identically to a Thunderbolt 2 port on previous generation Macs - e.g. you cannot plug a Mini DisplayPort display into it. Thunderbolt displays do work with it though.
Also, the lower-end 12" MacBook that Apple sells with a single USB-C port is NOT a Thunderbolt 3 port, so you have to know which devices that have identical connectors will work with it. Apple makes the distinction on its peripherals by screenprinting a little Thunderbolt logo onto the cable/connector housing. The messaging was reinforced with corresponding Thunderbolt logos next to the connectors on previous iterations of the MacBooks - making it obvious that these ports were not just Mini DisplayPorts but also Thunderbolt ports - but the new 2016 models don't appear to have anything like that on the hardware.
Additionally, there are USB-C cables and Thunderbolt 3 cables. Thunderbolt 3 cables are apparently higher-spec and will always work as USB-C cables, but the opposite is not necessarily true.
The ports are all Thunderbolt 3 ports, which I believe by definition means they are USB 3.1 ports as well. But some devices out in the world have USB-C ports that are not Thunderbolt 3 compatible. No longer can you tell what sort of devices will work with a port by its physical shape. For instance, I have a Windows desktop machine with a single USB-C port on the back, but it's not a Thunderbolt 3 port. So while I could physically plug in a Thunderbolt 3-only device, it wouldn't function at all.
Thunderbolt 3 is backward compatible with Thunderbolt 1/2 via an adapter, but the Thunderbolt 2 adapter that Apple sells does not function identically to a Thunderbolt 2 port on previous generation Macs - e.g. you cannot plug a Mini DisplayPort display into it. Thunderbolt displays do work with it though.
Also, the lower-end 12" MacBook that Apple sells with a single USB-C port is NOT a Thunderbolt 3 port, so you have to know which devices that have identical connectors will work with it. Apple makes the distinction on its peripherals by screenprinting a little Thunderbolt logo onto the cable/connector housing. The messaging was reinforced with corresponding Thunderbolt logos next to the connectors on previous iterations of the MacBooks - making it obvious that these ports were not just Mini DisplayPorts but also Thunderbolt ports - but the new 2016 models don't appear to have anything like that on the hardware.
Additionally, there are USB-C cables and Thunderbolt 3 cables. Thunderbolt 3 cables are apparently higher-spec and will always work as USB-C cables, but the opposite is not necessarily true.