I just got a thunderbolt monitor and excitedly, I plugged my early 2011 thunderbolt port equipped 15" Macbook Pro (running 10.8.2) into it and... no image on the monitor.
Ok, so I know that the TB display works because I plugged a mid-2012 13" Macbook Pro into it (running 10.7.5) and it works perfectly. In fact, I'm using it to type this message right now.
- in both the displays preference pane and about this mac/system info, the 15" mbp recognizes the display, yet... no picture either clamshell open or closed. restarted with it plugged in and not plugged in, no difference. also? sound comes through the monitor.
- ALSO, i plugged in a mini displayport monitor into the 15" port, and it displayed fine, so the port seems to be doing something.
It should just work - if it's not working with your 2011 model (works just fine with my 15" late 2011, right out of the box) I would get in touch with AppleCare as soon as possible and see what the senior techs may have to say...