I've played it.

I'd say everything but the story is pretty well-translated in comparison to the original Final Fantasy. In the case of the Demiforce translation, weird things like Basuna as PEEP and Scourge as AERO just seems confusing to me.

As for the story, it's translated well enough that you can understand what's going on, but there are lots of weird grammatical errors like said above. In all fairness, the pictures tend to highlight only the most egregious cases, but there are still plenty of them. I think they were trying to characterize Guy as having a primitive syntax but in combination with everyone's else errors it doesn't come through.

The translation does have a bit more of an 8-bit Nintendo-y vibe to it if that means anything. I played the Japanese version afterwards, and I got the impression it'd be pretty difficult to fit in all of the text into an English NES translation without compromising.