In a thread somewhere, there was a comment stating pilots flying large/heavy jets at high altitudes should hand-fly some to get the feel of how the aircraft handles. While I have fair experience flying a straight wing in the low flight levels, I am wondering how a swept wing handles in rarefied air. Is it akin to flying a small airplane near its service ceiling (semi-slow flight, sluggish to control inputs, unforgiving of uncoordinated flight)?

Thanks
J