I got a pair of these based on reviews and price. I needed to connect my Mid-2012 13″ MacBook Pro and a 27″ iMac to external monitors and hoped these would work well. So far, they are working great. They feel pretty solidly built. They fit the Thunderbolt (aka Mini Displayport) connectors firmly so far they’ve worked immediately with no initial issues.
The only potential issue I’m monitoring right now is one of these I have on my 27″ iMac, the connected external monitor occasionally blinks on and off. This happens maybe once a week for a minute, tops. Still haven’t confirmed if this is an issue with the monitor, the VGA cable I’m using, the iMac itself or this adapter. In this instance, it is a third monitor on this setup as my iMac has two Thunderbolt connections.
The other one I use alternately between a standard Sony PC monitor and an LCD HDTV in a conference room using my MacBook Pro, and no issues there. Good quality picture (as long as I use a good, shielded VGA cable with it – I had some minor ghosting which I determined was an old, crummy cable).
UPDATE: 1/30/15: I have confirmed my earlier issue with picture as being a defective adapter. It has since also started causing ghosting or almost “interference-like” issues that made the unit unusable. So of the two I bought, only one worked. Over time, with regular use, the other adapter that does work has started feeling less solid. I now find myself having to be VERY ginger about plugging and unplugging it because it feels like the cord is going to separate from the plug.