It would really help a lot if some tools do not use Grid snap while the latter is active globally. for example, it’s extremely disturbing that Grid snap is very aggressive while adjusting the control points of a blend curve or blend surface while still in preview. Maybe a tickbox (either in the pop-up window, or the Rhino options > Grid, or a Command line option called “Ignore grid snap”? 
Also, I would like to see another improvement in this regard. Add the following options in Rhino options > Grid:
- Ignore control points (already mentioned above).
- Ignore points.
- Ignore curves.
- Ignore surfaces and polysurfaces.
- Ignore meshes.
- Ignore annotations.
That will let the user choose more precisely which object types will obey the Grid snap and which will be completely free to move and rotate smoothly.
Another request regarding Grid snap:
Allow individual settings for the X, Y and Z axis (separate settings for the World and CPlane coordinates). For example, Grid snap to every 1 mm along the X-axis, every 7 mm along the Y-axis, and every 25 mm along the Z-axis.