Yes, it works very well. I've connected a 2009 Macbook up to my new Dell U2711 monitor, running at 2560 x 1440, 60hz. The Dell is a stunning monitor. The easiest way is to get a mini DisplayPort to DisplayPort cable which is available from Circuit Assembly (
http://estore.circuitassembly.com/products/Mini-Displayport-to-Displayport-Adapter-Cable.html). I found that I could then use the Dell U2711 as an extended monitor running at 2560 x 1440 connected to the Macbook. If I tried to mirror the Macbook to the monitor then the U2711 would drop to a lower resolution or crop the display so that less of the screen is used (obviously this is less than desirable). They way I found to get around this is to leave the Macbook closed and use an external keyboard and mouse (in my case these are the wireless versions). Now I can run the U2711 at full resolution (2560 x 1440) with Macbook fully visible on it.
Hope this helps.