Never send anyone to MrHappy unless you can't stand their guts.
I feel like hating on this guy is more memetic than an actual legitimate thing.

Never saw what the deal was with all the hate, and I actually find his guides to be the most comprehensive and helpful overall for the few bits of extreme-level stuff I have bothered to try when it was still relevant content. Many other guides I've seen for the same pieces of content aren't as thorough and tend to leave me feeling like there are potentially troublesome spots that the guide dismisses almost as an afterthought or doesn't even mention at all when I actually attempt the fights.

Yes, sometimes there are mechanics that are later discovered to have easier solutions for handling them, but that really happens to just about every guide-maker I've seen at some point or another so I don't think that's a fair criticism to use only against him and not anyone else.