Well, Dave Pensado knows his stuff and I'm not about to suggest I know any more than him. However, I'd venture it depends on the context of the praise - if he's saying he uses it as a rough guide on the main bus when mastering is going to be taken care of later by someone else and is likely to be brickwall-loud, that makes total sense. If he's saying he uses it all over everything all the time... well, his chops are better than mine!
Any limiter, by definition, is not transparent - otherwise it wouldn't be doing anything. Personally I like my mixes pretty dynamic and I am NOT a fan of incredibly loud masters - I listen on a system with a conveniently placed volume knob. Hence FG-X isn't to my taste, as I find it too extreme in the effect it has. I have other options (Waves, Sonalksis, Melda, more) that I prefer. Not saying the FG-X is bad, just not my thing - I don't think it's supposed to take the place of SADiE, either.