We also have the GM all weather cargo mats in both our Vibes. As a matter of fact, I ended up ordering 2 more last year to protect the backs of the rear seats in both Vibes when they're folded down. They've also worked out well for when we have our 3 dogs in the Vibes. I flip the mats over because the backsides are much smoother (and I figure easier on the dogs' feet) and easier to clean. The mats keep them from sliding around on the plastic in the cargo area.
FYI, you can get the GM all weather cargo mat (#19170827) for $79.80 + $8.95 (handling) = $88.75 from GMPartsCenter.net
. There are also currently two for sale on eBay
(they are both slightly more expensive than the one from GMPC though).