If you want to ride the tram (which you will unless you're feeling really fit!)... Or be willing to get a taxi to the top instead (which lots of people seem to do when they see the lines waiting)
I went at 8am, just after opening and had the carriage to myself... An hour later when I got back down it was packed!
But early means no shops open (which I was fine with) but if that would be a disappointment to you then maybe wait and brave the crowds.
It's definitely worth doing, if I went again I would go at night to see the skyline in all it's glory... It was fairly hazy in the morning with the sun and the smog but still amazing to see.
There are some nice trails to do in the park at the top, with joggers and dog walkers to keep you company.