Frequent delays. Poor frequency. Weird routes. Slow average speeds that can barely compete with a bus. Always getting bogged down by track-sharing with freight.
The Northeast corridor is the only section of the entire system that is even remotely decent and is basically subsidizing the crappy lines that they are congressionally mandated to run so it’s not even that cost competitive with other modes.
To be fair, most of this isn’t Amtrak’s fault but just a reflection of the fact that America doesn’t care about passenger rail.