I recovered from a bad crash once with Co Q-10. I think the important thing often is the dosage, to restore whatever functional deficiencies in mitochondrial function exist and can be restored, and then there's a ceiling above which you won't get much benefit, but maybe even harm.
In my case, I had 200mg. caps, and if memory serves had been taking half twice a day even during the crash, but it wasn't having any noticeable effect. Or to clarify, I had been taking it for months/years before that and had gotten improvement from it, which I noticed would gradually diminish over a few weeks when I stopped taking it, and so I started taking it again and just stayed at that 100/100 "plateau" or "ceiling" dose.
A few weeks after the crash and having gone through a bunch of things that didn't seem to help, I thought I would increase the coQ10 to 200mg to see if that would help, and right away within about an hour I felt 75 percent better. That's with my @ss dragging for weeks. There was a definite improvement, no question at all. Then I would take 100mg again in the afternoon, 200/100 again the next couple of days until I was much better, basically back to baseline, then gradually I decreased back down to 100/100 again and maintained there. So it definitely can have an effect, depending on what your particular metabolic profile or needs are.
Now since the immune activation that worsened the CFS last year, and the CHF symptoms are also worse, I wouldn't dare take anywhere near that amount. I just started taking about 20mg. a couple days ago, because too much and the heart starts pounding a little for a few hours, and then when it wears off there's a negative rebound effect where the heart feels much weaker for a few days. So especially if you seem to have the cardiac/left ventricular, etc. dysfunction that Cheney talks about, you have to take it very cautiously. I can totally understand why Cheney doesn't recommend it anymore. It can help, but it can also be a double edged sword and cause problems if you overload the pathway that apparently the co Q10 is activating (complex II or III, I think, maybe even IV a little, but I don't remember offhand). Maybe oxygen gets shunted off the ETC and causes the problems, or maybe it's a direct effect of the coQ, I don't really know. All the methylation blocks, etc. that Rich talks about are undoubtedly also implicated at some level, maybe even primarily. Fix those, and maybe even a few hundred mg. would be okay. With the immune CFS it doesn't seem to be, though - for me at least.
Btw, after trying a bunch of different brands (Country Life and some "gelcap" type that I forget what brand it is are two that I remember), since then I've always used Jarrow Co Q10, because it worked the best and was the least expensive per mg. and seems to be of good quality. And those are powdered capsules, so I think (or rather, I know - for me, at least), that the idea that powdered forms are ineffective is not correct. That's not to say some other form of delivery might not be even more effective, but as long as the dosage is optimized (meaning to what the person requires, not to a particular milligram amount), the powdered form definitely works fine. I can detect the effects of even 10-20mg of the Jarrow, so I would say it's a good brand and powder is not a problem.