During the workweek, our first Mass is at 6:45 am. It's really my favorite, because it's usually quiet and reverent, and there is only one paten and one cup without extra vessels to fuss over.
Right now is also my favorite time of year for the early Mass, when the beginning is at about dawn. It just seems to make sense to me to prepare and open the church while it is still dark and then have it be light at the end of Mass. It's so peaceful to walk into the church around first light--what I always understand by the summo mane of the rubrics of the Liturgy of the Hours--and greet the Lord in the Blessed Sacrament in the mystical and quiet darkness. That's just the way I've always felt as a praying person; prayer to me is a kind of blessed darkness. That's one of the reasons I was so grateful to discover John of the Cross, who speaks of the rayos de oscuridad, the "rays of darkness" that shine upon us in contemplation.
On the other hand, to have it still be dark out at the end of the early Mass, as it is in the winter, is just depressing. That's why this time of year, and I suppose its opposite in the spring, is my favorite time of year for our early Mass.