Node editor lagging / unresponsive and imprevisible Moving and arranging nodes has been a pain from 2.68 when I started using blender. With official and other builds. I have inverted the mouse to use LMB for selection and translation which is aggravating: RMB still works!?, still laggy, but for LMB I have to wait with mouse pressed over a node ~1/2 sec to be possible to drag the node. Otherwise simple click is not selecting the node. After successfully selected the node remains behind the mouse at every move.
Moving a node close to any margins of the editor window snaps the node far away on the grid, outside of the visible area.Which is especially annoying when creating new nodes as they get generated usually close to the borders.
Also the create node menu is slow to display.
This situation is the same on 2 computers that I use for graphics and is not depending on viewport shading.
I post here just in case someone has a suggestion to test. If not I will submit the bug.
Thanks
Yes!It was my fault from the beginning.
At some point long ago I have changed these settings in Preferences/Input
1.The lag is caused by Drag Threshold and Tweak T. With 3px (minimum allowed) the lag disappears. I supposed &amp; tested that their function is to smooth out drag behavior in mesh editing and slider controls but did not expect to affect the nodes in the editor.
2.The snapping was by Continuos Grab which I use also in 3dMax. And that behavior in node editor is a bug.  


  Drag Threshold
      The number of pixels that a User Interface element has to be moved before it is recognized by Blender.
  Continuous Grab
   Allows moving the mouse outside of the view (for translation, rotation, scale for example).  source: http://wiki.blender.org/index.php/Doc:2.6/Manual/Preferences/Input