No there are generally no problems using MediaLab (or DirectRT) with larger monitors. There are some issues that arise from screen resolution though. For example if you show an 800x600 image on a 800x600 screen it will take up the whole space. On a 1600x1200 screen, it will take up just 1/4 of the space. MediaLab is generally resolution independent but it does not stretch images, movie files, or HTML content automatically. Most of this isn't a big deal--it can just require some tweaking of existing experiments if you want them to look exactly like they did on your older monitors.

You can also avoid this sizing issue by running the larger monitors at the old resolution (e.g., 800x600) but then you would lose much of the aesthetic benefit. Personally I don't like that solution but it can be a quick fix if you need to get running ASAP. Note that doing this typically does not work well with wide screen monitors--just bigger ones that have the traditional 4:3 width:height ratio.

Hope that helps. You could also try a search on forums here with therms like monitor, display, resolution and the like for additional info.

Hope that helps!