I have the DVR-106, external,USB,1394 combo. i am having problems burning but I think it is the media. I have heard only great reviews about this burner.
I have the Pioneer 106D in a USB external case and it works great. I'm using Ritek (Ridata) G04 disk. I updated to the latest firmware by >NIL and able to rip it a lot faster.
Here is the link on >NIL's page. Don't open UPGRADE.BAT inside the ZIP program, but make sure you extract the whole files on your hard drive before you run the UPGRADE.BAT. I updated my firmware in a external connected to USB from 1.05 to 1.07 without a problem. Hope this help you.