The technology is old, but it's solid. It's never crashed on us while working. I think the only time they reboot it is at night when traffic is low and they do an update, but it's seemless because there are two systems. They update one and switch us to it, then update the other.

I work in an Air Route Traffic Control Center, not a tower.

If you asked me that a couple of years ago, I would say being able to talk with the pilots, but now the airlines are starting to adopt CPDLC which allows us to send text commands (to climb, turn, etc) rather than relying on voice communication. Not everyone has it though.