log_me_in wrote: … Why isn't it instantaneous?
Oh-- an entirely different question from what I thought! For me, the time can be pretty quick, but the files I'm interested in are usually relatively small. For portable devices, like iPhones, iPads, and MacBooks (you didn't say what sort the other computer was,) since syncing uses the battery, and since lots of people are very anxious about battery drain, the they will avoid syncing when not plugged in. And since syncing uses processing power, and people hate slow downs, they will avoid syncing while you use them. And since syncing requires bandwidth, they will avoid syncing when the internet connection is weak.
So, if you want faster syncing, then find good wifi, plug the devices in, and leave them alone. All this applies to a lesser extent for the desktop Macs.
If the devices are close and I really want the transfer in a hurry, I use airdrop.