I'm using a PX-708A with DVD+R Verbatim disks.
But its very slow.
First of all, make sure you use at least growisofs 5.11. 5.11 addresses
DVD+ performance problem with Pioneer unit, but later it became apparent
that Plextor unit would exhibit same performance degradation. If you
already use 5.11 or later, then I can only tell that I've had received
report from another PX-708A user, who reported that recording goes with
varying velocity and significantly slower than expected. Reportedly the
problem just disappeared with kernel upgrade [from 2.4.18 to 2.4.22 in
his case]. The [subtle scheduling] problem is most likely IDE chipset
specific, as there are more reports that the unit performs as expected.