I tried to open DWG file directly from QCAD. It tries open but hangs afterwards. I tried to convert the dwg to dxf. Still the same problem exist. I am using Ubuntu 11.1 and QCAD 3 is run using qcad script file. (Not installed). I used any dwg dxf converter which in turn run by wine.
Otherwise, the improvement from QCAD 2 to 3 is good. Auto Snap works fine.