Fine tweaking of spline points can be an ugly process - when you grab a spline point to drag with the cursor, it moves in discrete jumps, almost like there is a tiny little grid its snapping to. To avoid this I have been using the X and Y spin box in the property manager to make my fine tweaks for the selected spline points, but its sort of a pain to have to change my spin box increments down to .001" to get the fine tweaks I need.
Well, good news - if you hold down the CTRL key when you drag an existing spline point in the current version of SW, it will move quite smoothly. After years of being broken, SW finally fixed the sketcher so holding down CTRL disables inferencing when EDITING sketches like its supposed to (up till 2003, it only worked when CREATING the sketch contour in the first place).
If I remember my prior conversation threads correctly, Paul Salvador will be quite pleased.
I think the spline points move smoothly using this editing technique because the sketcher doesn't have to stop to calculate all around for potential inferences. The only real drag about this is that you have to be sure to hit the CTRL key AFTER you select the spline point - SW already has a copy-drag function in the sketcher that utilizes CTRL>then>select (which brings up another handy sketching tip for the new guys : CTRL select one or many sketch elements, then drag off while still holding the CTRL key, to make a copy of those elements within the same sketch. One of the faster ways to make lots of parallel lines in those situations where a pattern would be stupid and you can't easily inference them)
Extra tip for newbies - when editing splines, be sure to RMB click them and show curvature. This will give you real time feedback on the smoothness of your spline, as well as help you try to match C2 continuity with other sketch elements