I just got one of the official cargo liners from mazdagear.com.
Overall, I am not impressed, especially after waiting for this part for months. If anyone is interested, I'll take some pictures.
It is 5 separate pieces. The two seat back pieces attach with velcro to the carpeting, but they also require you to drill holes into the seat backs (4 places total). There a two smaller, rectangular pieces that cover the "flaps" at the base of the fold down seat hinge joint - these attach with velcro. Finally, there is one large piece that covers the rearmost portion of the cargo area.
My complaints:
1. None of the pieces seem to fit very well, I'm left with big gaps everwhere. The worst is the rearmost piece, which I honestly thought was for a different, smaller car when I first installed it. The piece doesn't cover the entire rear portion of the floor: there is a big gap in the right corner, and the left side corner is not covered at all (3+ inch gap). I'm wondering if the high end radio has a subwoofer in this position or something, but I only have the base radio.
2. The plastic looks cheap. It shows dirt and scuff marks like it is proud of them. I just installed it and it already looks filthy.
My advice: don't bother. Buy something else. I'll probably keep it, it will keep dog hair off the carpet (mostly), but I am very dissapointed. In my opinion, it is inexcusable that this part doesn't fit. Mazda should know what shape is required to fit perfectly.