Where it gets useful at consumer level is when your phone can hit WiFi and 4G simultaneously, so you can aggregate. And it's even more useful when both WiFi and 4G are iffy, so you seamlessly use one, the other, or both.

And yes, if both of your servers have to gigabit NICs, you can get 2 Gbps. But only if those uplinks aren't bottlenecked at 1 Gbps at the rack or data center level.