Support for MS SQL Server 2008 in QGIS is coming soon. A native QGIS provider for MS SQL Server is currently being worked on to make using, managing, and editing SQL Server data in QGIS just as easy as PostGIS.
The work is being sponsored by the Australian company Digital Mapping Solutions. So a very big thanks to them for this great feature!
There is no ETA on when it will be added to the main QGIS build, but the provider is currently in testing stage and hopefully will be in there soon.
So if you have been itching to try SQL Server data in QGIS, hang in there as a good solution is just around the corner.
P.S The other blog posts on this topic I used ogr, this method will still work fine after the native provider is added, however the native driver will add a nicer interface including integration into the QBrowser, better optimization for the QGIS code, and hopefully same feel as the PostGIS experience.