See my initial review here. I really like the glass for these smaller frames. The extra weight isn't an issue at this size and I'm always so nervous when working with Plexi for fear I will inadvertently scratch it. Glass also doesn't collect static as much (cat hair is a major problem at my house).
I see Framatic has corrected their instructions regarding the adhesive tabs. Unfortunately the adhesive provided was not strong enough to support even a small piece (7" x 9") of 3/16" matboard. I'm not quite sure if it was the weight or the paper on the back surface of the matboard that was the problem. Either way it's of concern so I chose to use another adhesive I had on hand. For larger pieces I wouldn't bother with the tabs at all and instead use acid free foamcore in the traditional way.
July 6, 2010~Update: Framatic no longer produces the bronze floating frames which I show in the above images. The only colors now available are silver and black.