I find that double-tap to wake is more convenient while it is sitting on a flat surface. If I'm already holding it, then hitting the power button is easier than using a second hand to turn it on. Tapping it while on the desk or table, however, saves me from having to pick up the phone.
I find that if it's been sitting on the table for a while, sometimes a single-tap, wait 2 seconds, and a double-tap will work every time. More convenient if I've got my hands full and the phone is on a counter (perhaps one hand dirty while cooking in the kitchen, and the phone has the recipe on the display).
Usually, though, it wakes 1st try without that trick, even when resting on a table.
EDIT for an Update: I have learned that if you have "glance" on our phone, and wave your hand over the face of the sensors to wake up glance, then the double-tap will work afterward while the glance screen is available. This is, of course, after sitting no the table for a while.