@Krzysztof - in Inkscape 0.46 and 0.47 the duplicated node(s) are selected after the command is executed, not like currently (Inkscape 0.48+devel r9834) the originally selected ones. Or differently phrased: in current trunk nodes appear to be inserted in the reverse direction of the path (towards the start) whereas in previous versions nodes had been added following the path direction (towards the end) - determined by the content of the selection after the duplication.
One main usage was to continue an open (sub-)path from within the node tool by duplicating the end node and moving it away (e.g. with the cursor key).
Is there a reason for changing the behavior or would it be possible to make the command act identically to previous versions?