I'm training in IS all the time - I've met both Mike & Dan as well as having trained with Ikeda sensei a fair old amount over the past 10 to 15 years.
We have 1 class a week dedicated to IS as well as using it within our aikido (or trying to) during all normal classes (that I happen to be teaching).
I'm still doing it because I now get what Ikeda sensei does and how - not that I can do it all obviously but I 'get' what he's doing. For me, it was Mike Sigman that explained the ABC's exceptionally well and gave me a far greater understanding than anyone else so far and it was Ikeda sensei that pretty much made me look into this stuff, I wanted to be able to do what he does, simple as that
.