Latency is a dependent on how far away you are from the datacenters and Google does have many datacenters. You can play Destiny 2 for free on Stadia to see what the latency feels like on the service. Also there are differences between games it seems with different games experiencing different amounts of latency. The Division 2 and the Doom games are some of the best games in that regard on Stadia.

I'm running it in the country in the Midwest with 100mbs down on a mesh wifi and it's practically flawless. Not any noticeably different than when I lived in Chicago with a fiber connection.

It's impressive and way better than I thought it would be when they first announced the product.

I recommend people try it out for free and judge for yourself.