Have you ever started the Fillet or Chamfer command, made two quick clicks, and realized too late that you had the wrong radius or distance? Yeah, me too.
To help keep that from happening – because who likes to redo work? -- AutoCAD LT 2012 added a preview to both the Fillet and Chamfer commands.
Now, after you pick your first object, you can hover your cursor over another object to see what the resulting arc or bevel will look like:
If it’s the wrong size, you can type R for radius (or get it from the dynamic input drop-down) and enter a new value.
And if you’re using the Polyline option of either command (which applies the fillet or chamfer to all segments of a polyline at once), you get previews of all the new corners just by hovering the cursor over a polyline.
Again, if you need to change the fillet radius or chamfer distance/angle, you can do it here, before you finish the command and need to undo and redo it.