As for ki aikido (to keep on-topic), I don't think it's failed any more that any other aikido, but do I think the Tohei world-view will become a bit dated if the IS stuff gets successfully integrated.
IMO, it's just like anything else in martial arts. There's a difference in doing things and doing them right. I mean he did that stuff. O'sensei did some of it as well, which is where he got a lot of it. It seemed to be part of his routine. Some aspects of it also exist in people like Sagawa's tanren. I don't think it's going to make you an IS superstar or anything, but stronger aikido, definitely. Again though, we're talking about doing the stuff properly and not just going through the motions. That includes all the ki testing stuff in the taiso as well. Even modern ki society people could be going through the motions. Then though, even if you have someone doing the stuff right, with the right focus, right intent, how much of it are they doing? Doing it for 15 minutes before class a few times a week isn't going to do much. We don't really have much insight into Tohei's personal training routine, but it's probably safe to say that he did a good bit of training off the mats.