I've only used them occasionally and only at low level, and neither of my last 2 groups that I DMed for chose to hire any.
We use them all the time. My games are dangerous, and you never know when a henchman gets a battlefield promotion! Plus you get to do things to the henchman that might seem unfair to a PC. "Henchmen taste like chicken", as Pat says. I love chicken.
You forgot the "ab" before the "use" in your poll answers
Pat, that made me smile.
I'd never really used them until I started playing Moldvay D&D with the NYC Red Box people. We used them (and a houseruled category of retainers called "zealots" - religious fanatics that follow clerics for little or no pay) nearly every session.
I voted for only at low levels. At high levels I can't stand having all those people following me around. I wanna play an rpg not a flippin war game.