SA Replay hotfix reduces some jittering, a decent gaming mouse with a good software is also preferable, turning the OS mouse acceleration can also improve your smoothness. Use the lowest sensitivity you're comfortable with at first & work your way up from there, make sure that you have a decent, large mousepad, or at least a some sort of matted surface. You may also try recording with 10 fps, instead of 15/30, that seems to reduce the unsmooth movement, although you will feel it strongly when recording. Pay attention to the space that's available to you, learn to stop when necessary, don't try to keep the angle in constant movement, that may really impair the actual angle & make it uncomfortable for you to work it out. It might seem at times that if you stop moving the angle once started, that it will break the flow of the angle, this is not true, learn to ignore that idea. Should it occur, you can always create movement with pan/crop afterwards.
Hope this helps.
