hmm, tried it on my computer, wasn't really jurkt, maybe it was just because your mouse was visible. The mouse movement normally makes the illusion that teh camera is jurky! anyways you could try using the curve angle function, so your code would become:
rem obtain mouse coord.
cx#=wrapvalue(cx#+mousemovey())
cy#=wrapvalue(cy#+mousemovex())
rem smothen cam coord.
x# = curveangle(x#,cx#,1.5)
y# = curveangle(y#,cy#,1.5)
rem update cam.
rotate camera x#,y#,0
hope that helped
your birth was a blessing, sent to live and die on earth as a lesson, we each have a star all you have to do is find it, once you do, everyone who sees it will be blinded - DMX