I've got a Dell UltraSharp 2913WM 21:9 aspect ratio 2560x1080. Personally... I love it, it takes a while to get used to the very wide aspect ratio though. I bought it to replace 2 1050 22" LCDs and it does the job flawlessly.
As for game compatibility, I found some games work without problems, others have no support for 21:9 resolution, and others have either aspect ratio issues or HUD issues.
As for the first case, I played BF3, Dead Space 3, Borderlands 2, GRID 2, FarCry 3 and Torchlight 2 with no problems at all.
Second case, I can't really remember but I know I played at least one that failed to have 2560x1080 resolution.
Third case, Skyrim (Top and bottom of HUD goes off screen) used "Flawless widescreen" to fix it and RidgeRacer Driftopia stretches out everything.
My take is that most games work with no issues or minor issues like FOV scale.
Lastly, even an old game like Unreal Tournament in OpenGL (DX7 doesn't support such high res) works amazingly well, I just needed to change the FOV to about 120.