It did help me.
The problem is not so much whether the art itself helps, but whether the teacher teaches it in a way that helps.
More specifically, when I started out with Aikido, my first sensei taught the Nishio style. You can look it up on Youtube, there is a full DVD with the original Nishio guy to be found there. The specialty of Nishio is that he includes sword work in the usual training, a lot.
We did not actually do that part, i.e., regular training was usually without katanas. But we did a lot of katana and stick work on the side. Sometimes katas, sometimes partner exercises.
The katana partner exercises were often frustrating, as it was hard to get a sense of "would this really work" or "would this be tactically sound", and I did not really feel that it transfered much, anyways. But I loved the katas (which are very similar to Iaido, if not exactly the same). Our teacher really went all out stressing the timing issues around the longer katas - when to be quick, and when to be slow; when to relax, how to breathe and such; and was very detailled on exact execution of the movements.
The katas, especially the long ones, have little to do with actual Aikido exercises, but it helped with getting the mindset of really listening to the whole body; balance, not extending yourself, being in control of your own motion. I apply that a lot during regular training these days (I am not with that sensei anymore, and at a dojo which does another style). Also, in many exercises, there are instances where being able to imagine doing a sword strike really helps the correct movement (i.e., most 45° spiraling downwards movements are so simply done by imagining a yokomenuchi katana movement that is being pulled through - people who do not have that mental image can struggle a lot).
So give it a try, by all means.