Love 'em - whether in F or Y, though obviously F helps. Gives you more time at your destination or gets you home to loved ones quicker.
Key always for me is to find the longest overnight leg, e.g. LAX-ATL go via SFO not ORD to get an extra hour sleep.
Worst red-eye - DEN-ORD arriving 0200 - and then a 0600 ORD-ATL.