Thanks for the response.
I'm currently deciding between the U310BT and the Kenwood Excelon x993.
The Pio is about $150 more, depending on where you look, and MIGHT be worth it for the bling bling of having a double din screen for (theoretically) easier navigation of USB/iPod/iPhone controls, NAV, etc.
Does the U310BT do a good job of reading from USB flash drives? ID3 tagging supported, reads and loads the files properly, etc?