I've never succesfully sustained interruption tracking. Only a few timers support it, and the ones that do are the ones that try to be a task manager too. Since I already have tasks tracked elsewhere, I've never wanted to use the very rich Pomo software packages and just chose not to track them, instead.

Similarly, I don't tend to feed back the actual duration info into my system. I could--my task tracker has an estimate field I don't use since I estimate in numbers of pomodoros, so I could put real times there. But I doubt I'd look at them so I haven't bothered. So I don't necessarily get the benefits Pomodoro outlines re: making estimates better. I do think that having to break stuff down into sub 2 hour (and preferably sub 25m) chunks has helped me there, but it's an indirect benefit.

But the timer itself is invaluable.

I have ADHD and anxiety issues, and big tasks get intimidating enough that I have problems starting them. I was already using an "I'll put N minutes on the egg timer, then I can decide to bail if I want" technique to cut intimidation and get started. It's a very well-known way to get over that first hump.

Pomodoro just formalized that a little more for me: now I make that call at the end of each 25m Pomodoro. I invariably end up stringing a few together before I bail, so it works for me.