Can confirm, the commuter train here runs ~75 mph and is quite popular. Then again, it's competing with 70mph highway.

I have looked into taking Amtrak several times, but it takes 2-3x as long as driving, 5-10x as long as flying, is more expensive than both, and has far fewer destinations. It's a hard sell for anything other than taking a train for the experience or short distances. Trains should be cheaper than airplanes and faster than cars, but they're neither in the US...