Doing architectural stuff with Blender is not the easiest thing, as currently (i.e. until BMesh is out) Blender supports only meshes made by triangles and quads and architerctural work is easier if you can handle ngons (this is the reason why SketchUp is so intuitive, you don't need to think at the model and the mesh topology at the same time). On the other hand, Blender keeps growing at a furious pace and learning it is a future-proof investment.

Wings3D is much more limited w.r.t. of the kind of meshes you can manage (forget curves, planes and non solid stuff).

For CAD-like stuff, I am investigating QCAD/CADuntu, they seem quite powerful and really inexpensive (especially the free CADuntu ).

A program I have not tried, but I know lots of people are madly in love with, is MoI.

Bye!!!

GIMP 2.7.4, Inkscape 0.48, Genetica 3.6 Basic, FilterForge 3 Professional, Blender 2.61, SketchUp 8, PoserPro 2012, Vue 10 Infinite, World Machine 2.3, GeoControl 2