Well I just got my Viewsonic DLP glasses and was able to compare them with my IO Systems glasses on my Samsung DLP. I literally held the glasses on top of each other and just moved them up and down to compare. While the IO glasses certainly get the job done, and are affordable, the Viewsonics are clearly superior.
* No uneven dimming at lens edges like the IOs (creates some crosstalk)
* More comfortable
* Several size nose pieces
The quality and comfort difference is enough that I just placed an order for a second pair today. I'm not gonna knock the IO glasses too much though, they've worked well, they were quite affordable, and they were shipping when the Viewsonics were still vaporware.