I've been swapping email with Radial about the PZ-Pre, and their response to the lack if an XLR input (microphone connection) and separate tone controls for the second channel had to do with size; they said that when they were discussing design constraints with traveling artists like John Pattituci, compactness was at the top of everyone's list: The PZ-Pre is only 4 1/2" H X 8" W X 2" D.
I intend to work around its "limitations" by carrying a small mic-pre in my gig bag (they recommend a unit with headroom >20dB), and plugging an EQ pedal into the effects loop when I have two basses plugged in; when I'm amplifying upright with two pickups, or a pickup and a mic, I'm hoping that one set of tone controls will suffice when the two channels are summed.
On paper, the PZ-Pre looks better suited to my needs than anything else I've seen, and $280 seems reasonable. I sure hope it lives up to my expectations once it arrives.
Radial told me today that "PZ-Pres should begin to deliver in about two weeks." Their rep also told me that they planned to introduce a full-featured model in 2008.