Aside from the inconvenience of clearing immigration on transit (and I can't say I've ever transited _through_ the US, despite clearing US immigration ~50), the

Aside from the inconvenience of clearing immigration on transit (and I can't say I've ever transited _through_ the US, despite clearing US immigration ~50), the airport experience is much nicer. International and domestic flights can leave from the same terminals, go through the same security, and use the same in-terminal facilities. You don't have to go through an outgoing passport control, so half the waiting time. I'm very happy with the system.