I loved the instant mount cast option when it was added to their legacy system in SWTOR. The flow of movement from exiting combat is wonderful. Its like leaping on to your steed like some kind of boss whilst moving. Destiny 2 has it also and that is a must to get to the next open world target as the maps are large and if hunt trains are present you need to get their asap to get credit.
The flow is so nice that once experienced you wish it was a thing across all games where you can use a vehicle/creature to traverse maps without having to come to a complete stop before getting on.