If anyone is wondering how to get a full resolution (2560x1080px) from the LG 29EA73 on a Macbook Pro 15″ without spending a hundred bucks on the Apple Store, here’s a solution.
No need to buy from Apple a Mini DisplayPort/Dual-Link DVI that costs around 99 euros, just get a DVI to Mini DVI cable for 20 euros and it will do the job perfectly. Using a HDMI cable is apparently not enough for your mac to display a 2560×1080 resolution. Only DVI link can do that.
Hope it helps.