I knew someone who did go to a Diamond Way centre in Texas years ago. I'm not sure how it's structured, but I would be surprised if the founder managed everything, as they have dozens of centres. She said she didn't quite like the atmosphere there, and discontinued going.
As for my own experiences, about six years ago I actually didn't know about the Karmapa controversy at the time, and I joined a Facebook group about Vajrayana Buddhism which I eventually found out was Diamond Way. It seemed fine, until I eventually found out about the Karmapa controversy and asked about it publicly in one of their forums, and without notice I was booted from the group. I asked why and the manager of the group said I mentioned the name of the "other" Karmapa, whereas they were followers of Lama Ole and his Karmapa. I looked up the issue and found Lama Ole's comment on the controversy was that every teacher should be judged by the merit of their own teachings, and it wouldn't matter if there were two Karmapas (as a matter of fact, I found some of his lectures to be quite useful). So I quoted Lama Ole's comment to her and asked her if she agreed, she said that I was being extremely rude and blocked me (I really don't think I was being rude, I was just trying to reconcile). So, if you do go to a centre, it might be pretty good, but just be careful what you say because they may be a bit touchy about some things (though I may be being rude in suggesting that).
As for the make up of the centres, as far as I know they're pretty much all westerners, but they'll have some Tibetan lamas come from time to time to give lectures. At the Thrangu Centre I occasionally attend (which is said to be pretty conservative), it's kind of the opposite to Diamond Way (which is really like a westernised Buddhism), since it's probably 80% Chinese and Tibetans, and 20% westerners -- the catch is that the westerners all wear Tibetan clothing too!
But as far as the individual centres go, I'd evaluate each for it's own merits. There's great gems everywhere, and Lama Ole is pretty much right in saying that teachers need to each be evaluated for their own merits, not brushed aside or generalised as good or bad. So, might as well go for it - if there were one near me I might even go to have a look too.