Can you give me a bit more quantitative descriptions of "laggy as hell" and "unusable slow"? It should render with 2-3 fps, though certain settings can slow it down, e.g. the projection: Please switch to Mercator projection, that should improve performance. It will be default in the next version. To do that, open the application menu, choose "Map View" and change the projection in the top most input field. Also make sure to use the OpenStreetMap theme.

OpenGL support is planned for Marble 1.1 or 1.2, that's around April or end of 2011, respectively.