I don't do time outs. I started avoiding them because with my explosive older child, it would have turned into a physical punishment - I would have had to physically keep her somewhere - and I wasn't willing to do that, partly because of my history (toward end). Then I read Unconditional Parenting, and that resonated with me, and I started trying to think of other ways to handle her tantrums. I decided that for her, just letting her do her tantrum thing and then reconnecting when it was over was the best choice. It wasn't something she was doing to me, it was simply a loss of control, and it felt wrong to me to punish her for losing control when she wasn't trying to anyway, I decided. There have been times when I've been tempted as the years have passed by, not because I thought it would teach her something but just because I thought it would cause a behavior to at least end in the moment and that would be nice. But I've just tried to handle things as well as I could without them, and now she's 9 and is doing well. My younger one has never had a tantrum at 2.5 (knock on wood) and is the calm, easy child I'd read about when my older one was little, so it hasn't even come up as an issue with her.
So for me, I've done ok without them. I see why people use them though and I do think they can be used gently and as a part of GD.
I will add to be fair that I grew up in a home with a sometimes abusive alcoholic, and because of that I sometimes feel natural reactions that are outside of the reality of what my kids give me, and need to separate myself for a time being because, frankly, I feel an urge to hit them. So I briefly separate myself to protect them, and I don't doubt that has at times felt to them like they were given a time out as it's still a separation. But I've decided that's the best choice available to me at those times. The older one is well past all that, and the little one is quiet, so it hasn't come up in a long time, but certainly it was an occasional occurrence when the older one was younger. Though tantrums weren't a trigger for me - I found I usually just empathized with her loss of control. I can't remember what specifically triggered the feeling. It was probably more about me than them.