Plextor's taken a dive in drives the past few years, and I thought it was while they gear up for Bluray. Guess not.
I go to club.myce for drive reviews so that I can see the quality reports.
Here's a thread on the B940SA. The 1st post backs up that it's a rebranded Pioneer, but seems some quality issues and settings removed that the Pioneer has.
Not a lot of known good BluRay yet, as it's still settling out. Most of it is TDK, with Verbatim being good yet sticking to slower rated speeds...so I'm still trying to figure that part out.
The early Pioneer was good, but I'm pretty sure it was discontinued and replaced with a model with some corners cut to keep the price in check. The quality still appears good though, just some random read errors on TDK media.