Having 4 or 5 empty seats to yourself in a UA economy row is not a bed of roses. UA's econ seats have a bucket shape to them, making the experience a very lumpy one indeed, and putting the 5 blankets down to try and flatten things out doesn't really work well. Furthermore, the seats are very narrow, so you really can not lie on your back...

Sometimes late in the year when all of my SWUs are gone and I have a midweek flight to Asia I simply call SQ to check out their econ loads last minute. Often I can get 4 nice flat and wide seats to myself. ^