Depends on where you ride it. In the Northeast, trains ride on Class 7 and 8 track and can get average speeds above 80 mph. Elsewhere, the trains ride on Class 4 track (so mandated by the almighty federal government, i.e. to be the least expensive/most affordable for freight operations under the current federal regulations) and average speeds slow down to 40 mph or slower. Back when interstate rail travel was more prevalent, intercity trains ran at average speeds of 60 mph at least, which was best practice for the level of technology at the time.
In the late 60s, the federal government was promising 160 mph top speed for trains between New York and Washington DC. And they didn’t deliver; the first Metroliner had a top speed of 110 mph. 45 years later, they are echoing the same promise; it’s like time stood still, but that’s what happens when government takes control.
I haven’t had any problems with Amtrak. I’m not a frequent rider though.