The cohesiveness and balance (or not) of the rules can weight opinion in it's favor or damn it. But that doesn't mean that even perfectly written rules will be 'fun' for a given group of players. Candyland, for instance, is balanced (everybody randomly sucks the same). But it's not fun for anyone who wants to try and improve their game.
A lot of the angry/dissenting opinions that have been voiced by the competitive community concerning this 'Leak' seem to be focused on the more radical changes in the PDF to things like the turn structure. But GW has shown it's willingness to to radically change core game mechanics before. Witness 8th Edition Fantasy. While I and many others would call 8th a huge mistake, we have no way of knowing GW's internal thoughts on it's success. So all we can do is guess as to whether they were encouraged by the experience or took it as a dire warning not to mess with something that works.
But... Does 5th Edition 40K still work? That can be argued too. From GW's standpoint, that will depend on how the rules and models are selling compared to a few years ago. They've got long term goals and plans for the system. Which may or may not include competitive balance of the sort we got used to in 5th under Alessio. GW has shown again and again that it cares little for the competitive community, which makes up only a small percentage of their sales. Remember that most 40K and Fantasy players never leave the basement for the store.
Now look at Jervis' Throne of Skull tournament. See how convoluted it was? The guy that set that up is now in charge. Alessio and Priestly are gone. The design studio is only 3 guys plus Jervis writing rules now. That means the character of the organization has changed. So who knows what Jervis/GW have in mind. It's not as if Tom Kirby is likely to have a game design opinion past pushing model sales. Merge Apocalypse and 40K? SURE!
So I guess what I'm saying is... let go of your assumptions and your hopes. Assume whatever build you're playing now is going to have to change at least as much as the change from 4th to 5th Edition required. Accept that as fact. Then...
READ THE PDF!
Really. Read it through. Every bit of it. From the basic rules to the Stratagems and Apoca-crap. Then you'll be able to form coherent arguments about it. Either for or against it's validity. You can also decide if it's likely to be fun, which is a different thing entirely from whether it was faked.
Because if all you do is get 5 pages in and start ranting... Well, that's not productive, now is it? I'd like to hear some well reasoned and thoughtful arguments against the validity of this ruleset, but it seems like the only people who have fully read it are also coming down on the side of "Hmmnnn... not bad.".