Assimilation cycles in MSC's 3D-var analysis system are performed using full disks of GOES-08 and GOES-10 data every 6 hours. The impact of IM3 channel (water vapor) is analyzed for clear skies as well as above low clouds, the latter data doubling the horizontal coverage. The impact of the density of data is studied both in analyses and forecasts. Several studies are also conducted for the assimilation of surface channels IM2, IM4 and IM5. The impact on the boundary layer structure is assessed, with and without vertical correlation of errors between skin and low level temperature. The synergy with microwave AMSU-B data is evaluated. The "final" operational implementation strategy is presented.