DoubleCAD XT is (as its name implies) most certainly a full-featured CAD tool. It's more affordable than AutoCAD LT, and it "holds hands" with SketchUp better than any other CAD system on the market. Among other things, DoubleCAD XT:
- exports COLLADA files which you can open in SketchUp
- imports .SKP files natively
- imports and recognizes SketchUp layers
- generates viewports from scenes in your models
- converts components into DoubleCAD blocks automatically
If you're a Windows user who routinely creates 2D documents, you owe it to yourself to give DoubleCAD a whirl. The no-cost version DoubleCAD XT is free, and is extremely capable, and the Pro version adds lots for US$695.