This cable lets you connect your Xbox 360 to a computer monitor that has a VGA port.
If you cant afford a HD TV but have an awesome computer monitor, this cable comes in real handy. Moreover if you want true 1080p, you need a TV that has 2 million pixels, and these definitely don't come cheap. The other TV's that come in the $1000 – $4000 range usually have a 1080p sticker but if you look up the resolution, its going to be less than 1920×1080.
I've used this cable with a 19" Viewsonic VX 922 @ a resolution of 1280×1024 and on a DELL 2407 WFP @ 1920×1080. Games look awesome on both. If you can spend $700-$1000, get yourself a 1920×1080 monitor. If you cant, get yourself a good (recommend the best) 19–22 inch monitor.
If you guys are playing on your old BOX TV, you're definitely missing out on a lot of eye candy. Get yourself a decent computer monitor and get this cable.
The sad part is that its got only left and right channel outputs. So no surround sound. Sound quality is top class though.
Note: Its a VGA cable, so the digital signal is converted to an analogue signal which means that there is a slight difference in quality. If your not a person who can instantly pin point the difference in color/picture/image quality, you shouldn't be affected at all. Be sure to update your console to unlock all resolutions.
Have been using this for a year now and no problems so far. Hope Microsoft releases a DVI cable with full audio connectors.