Hmm I thought I responded to this thread earlier? Lol, anyway.
I had one of these with DD#2. I found it really useful, I actually had a need for it which is why I decided to buy it. I had a hard time with DD#1 keeping track of what happened when, and while I wasn't keeping her on a schedule, I still wanted to know what her schedule was, and I found it hard to remember.
I saw the Itzbeen while looking for something else online, knew I'd find it useful and I did. Like I said before, it wasn't so I could keep DD#2 on a timetable, it was just so I could keep track of hers. It was handy being able to just glance at it and know what was going on, instead of trying to remember or find a piece of paper I had written it on. I was so delirious from sleep deprivation (and the pain killers they put me on!) after both girls births, I needed all the help I could get lol.
I think for twins they would be quite handy, I think they come in different colours now, so as long as you either label them or get different coloured ones, you'll know who's is whos.
I've also found them useful past the point when I needed the timers, a quick distraction during nappy changes, or DD#1 using it as a torch/nightlight.

Lol I actually was using the light to read books under my covers when DD#2 was still in our room and I couldn't read with the lamp on.

Best of luck with everything, I hope it all goes well!