They added unit veterancy, 

fog of war

the AI is different

a new UI

new network code

you can switch between high res and pixel doubling on the fly

you can change the stance of units (defensive, fire at anything, do not fire, etc)

you can queue production of more units and buildings

Frankly all of the changes seem positive to me, just basic shit to keep it playable today.

There are still a TON more people playing on that other network with the original games though, this just looks superior to me, and is still being developed