Yes, always at a stop light, never while moving. Even if I fail to notice a green is coming on, which shouldn't happen so long as you look at the cross lights every few seconds, the most that could happen is you inconvenience those behind you. That's a better mistake to make than when you're moving and can kill someone.
And besides that, I've never missed the start of a green light. The problem with texting at a stop light is when people become so focused on their text that they neglect to check in on their surroundings frequently.