Latency is something Google already has a large, distributed network with low-ping datacenters to major population centers to address.
It's surprising how much latency a human will tolerate without notice, however.
I think that's only if we ignore monitor refresh rates. Most of us are maxed at 60 FPS which with a lot of hand waving is equivalent to ~17 ms latency. It's relatively easy to get a network with latency better than that. If you can achieve the rendering + data round trip in under 17 ms you're going to be functionally equivalent to a local computer.
So, I'd say that I'm running the best case scenario available within my area.
My anecdata counterpoint is that I pay for the cheapest/slowest broadband available in a midsized city and my ping to google.com is 14ms.