… it turns out that this technique is important using QGis 1.8 with tiled WMS.
You can set the following options on the wms connection properties:
1) Append this to the wms url "?TRANSPARENT=TRUE" or "&TRANSPARENT=TRUE" if your url already has more parameters
2) Check the option "Ignore GetMap URI reported in capabilities"
This works fine only if your capabilities doc does not point to some other location than the wms url you defined in the connection...
AND ALSO…
getting fine results with the new QGis 2.0. trying a few experiments now with WMS of PostGIS geometry layers.
AND ALSO…
Geoserver 2.4 now in place as well.. the block above cost me a lot of hours… grr