I use them! You have other issues going on with your 1st row to worry about tiles slipping half a mil. On my 1st row of tiles I like to concentrate on the tiles being plumb by using a 1800 level accross the face of the
tile with the edge of the level projected as far out as possible so I can assess where the true plane of the tiles will project, then make subtle adjustments with my rubber mallet, now, stuff doing all that and worrying if one of my wedges has slipped on the floor and my
tile has slightly dropped!... I love to know my 1st row of tiles is perfect as it makes the test of the job a pleasure to do!