I don't usually use it, but a couple of times I've found the 'pick rotated team' option quite useful. Sometimes I stare at a first XI who are almost all in 90-95% condition, and a load of squad players who are OK but not crying out for a chance, and I get a bit stumped as to who should be given a rest.
After the AM's picked a squad I often revert a couple of changes (e.g. to avoid having a completely fresh centre-back pairing, or so I don't have a midfield completely devoid of pace), but it's a useful starting point.
I hardly ever pick the same players in the first part of the season, because with European and League Cup games you have to rotate pretty much every game. It always seems to take until the second half of the season before I have a settled first XI.