I enjoyed it, if solely for Shoudai. If you have to be critical, the whole drama is a total crap. Yeah, it got a few nice cinematic scenes; the fighting, for the most part, is decent and authentic enough, considering the fact that the young actors did it themselves. But there a bunch of plot holes. I kept confusing Shoudai's boss with the dead girl in his memory. And the ending makes no sense. Although it doesn't piss me off but it keeps me wondering if Shoudai is still stuck in jail since he couldn't prove his innocence or that is just a stage for his revenge against the former mastermind of the game. No offense to Decade's fans but his acting in DPG is just horrible (though he was also bad in Decade, it was somewhat more tolerable). I cringed when he said "Bye bye", it was just... awkward and forced. When the actors can't speak English properly, the director should just stick with their own language (=_=!)
I think DPG is the kind of movies that you just have to enjoy by simply staring at your idols/favorite actors. To me, the casting seems to be based on the popularity of Decade and Shinkenger.
Edit: I just reread Kaji's post. It kinda makes sense that way. That explains the villain's weird death scene.