I would steer clear of these.
I have a bunch of TDK branded Ricohs that burn each and every time at 8X in my TDK 840G (a Plextor 708A, rebranded).
However these discs you mention, which are "arita", hardly ever burn at 8X. They say they are burning at 8X, but actually burn at 4X for the last portion of the burn. The average burn time is 10 minutes, sometimes longer. I get coasters about 25% of the time.
Now the discs that drop down in speed -do- work, but I can spend $1.20 a disc for the branded TDK discs (as I did at Staples this week by buying on-sale 25 packs, or as you can do starting Sunday at Best Buy for a 100 pack) - and know that I will get no coasters and 100% 8X burns.
YMMV, of course.
-P