I keep waiting for folks to realize that with the Batman franchise, there is room for many Batmen, just as there is room for many Jokers. This is a more youthful take on the character and judging it by appearance alone is a mistake.
That's why the reaction to him (and Batfleck) were so funny to me. If anyone is old enough to remember the extreme controversy when Keaton was cast as Batman - back before the Internet and folks were just discussing it standing around in comic stores - yet that made media headlines, the Twits posted about both castings today were like tiny little fan boy ripples in comparison, LOL. If it had been that easy to scream your complaints to the world in 1989, it would have broken the Internet had it existed in the form it does today.
As great as Ledger's performance was, like much of Nolan's Batman, it was missing some key aspects of what make the characters so timeless. Ledger's Joker wasn't insane. He was quite calculating and was an anarchist, but not unpredictable/crazy as the Joker is supposed to be. (Case in point - when Nicholson's Joker shot Bob the Goon it was a split second decision; when Ledger's Joker killed his goons, it was completely planned and premeditated).
Personally, while I thought the Nolan Bat-films were okay (the first one is rather boring, and Katie Holmes is so miscast it's a distraction, the second one is of course very good, and I actually quite enjoyed the third one because I felt Nolan finally made a Bat-character with Selina), they were missing to me the key elements that make up Batman. Particularly Gotham City - New Chicago just didn't do it for me. The gothic in Gotham is as much a character as anything else - and is the contrast between Superman/Metropolis (which is why Nolan's Batman would never have worked in a shared universe).
Suicide Squad could be crap - won't know till we see it - it wouldn't have been my next choice - but neither would Thor, Iron Man, or GoG have been my choices to make films out of, either. I'm willing to be surprised, and while folks are so centered on the appearance of the new Joker (which really isn't that extreme, it's not like they made him tan with blue hair), I think they are forgetting the fact that if they are going to get someone to play bat-crap crazy Joker as he is traditionally portrayed, they certainly picked the perfect actor to do it.