I've now added the initial revision of the OGR MS SQL Spatial driver to the GDAL repository. For further information please refer to the driver information page.
Working binaries (which always contain all the recent fixes) can be downloaded from the daily build system available at: http://vbkto.dyndns.org/sdk/
Since I didn't have the chance to test with all kind of the fancy spatial data types any feedback on the potential issues are graciously accepted.
Upon the experiences gathered when writing this driver, I'm also planning to add support for accessing the native SqlGeometry/SqlGeography serialization format in the MapServer sql2008 driver which appears to provide a significant increment in the performance of the data retrieval.