It can be useful but it's also annoying when combined with start/stop because you lose your brake pedal control of start/stop and it can end up stopping a lot for <5 seconds at a time, which doesn't actually save you any fuel (or so I've read) but does add unnecessary wear and tear
BMW X3 (F25) xDrive20d SE . . titanium silver . . titanium front grille . . 309s . . xline . . xenons . . black leather . . alu trim . . professional multimedia package . . dynamic package . . climate package . . electric seats . . folding mirrors . . servotronic steering . . DAB radio . . business speakers . . sun protection glass . . split rear seats . .