Below are the two adaptors I use that work fine.
I use the VGA at work for the connection to conference room projectors
I use the DVI connection to a $100 flat screen second second monitor I have
I'm happy with both. The only issue is, since I plug/unplug the thunderbolt cable several times a day, the connection moves and the monitor sometimes looses the signal for a second. Thunderbolt is just not a tight connection like DVI and VGA and doesn't hold it in place strong enough. Nice that its small but not a good connector over all...the number one requirement of a connection is that it is tight and secure...thunderbolt fails this.
I had a similar problem but wanted to use the HDMI port instead of the thunderbolt port.
I tested this on a MacBook Pro Retina (late 2013) and on a MacMini (2012).
As stated above, on both machines my HDMI -> VGA dongle did not work.
To solve this, I placed a HDMI repeater between the Mac and the dongle.
Surprisingly this does work.
Repeater: HQ AVREPEAT-31
HDMI->VGA: Delock HDMI-A male > VGA female