I'm interested in new techniques that will enhance the endgame. ATs give the game longevity and thus provide more fun to be had.
There's no reason why you should be scared of them. They're just an extra layer of depth to the game you have the choice of exploring.
But there in lies the "trouble" with ATs. If you want to stay with the flow of advanced or tourney-class play, you MUST at least know how to deal with them, even if you may not use them yourself (say, the character you use doesn't really benefit from the trick or whatever). Where's the choice, if you wish to remain at least a half-way competent player?
It's the same thing that happens with a number of fighting game out there. Some one finds some exploit, and that changes the game. Some people like it because it adds more to the end game, but, to me, it often ends up being more annoying because it's usually some stupid trick that becomes such an emphasized part of the "new metagame", you have to adapt to it, or else.
Take for example, Street Fighter Alpha(Zero) 2. The "Custom Combo" system was already something that was already screaming of being broken. But when a guy named Alex Valle discovered the "low roundhouse trick" it just made it even more of a thing that showcased the faults of the system that Capcom implemented in the game. After that, EVERYBODY starting using it, and it started to boil down more to who could utilize the trick better than his/her opponent. And, to me, that equated with boredom; the same type of boredom that I eventually had with the likes of SF3: 3S and "Serious!" Smash play.
Personally, I'd be happier if BRAWL turned out to be the "Super Street Fighter 2 Turbo" of the Smash lineage. There may be a number of BnBs here and there that make some characters great by default. There will probably be tiers, though possibly more even, where every character is feasible except in the most extreme circumstances. But it would never be such a thing that the game would eventually come to revolve around engine exploits, which then dictates the meta-game from that point forward.
Super Turbo didn't need exploits to still be a game that's been played for
OVER 10 YEARS, and counting. Neither have the likes of games like King of Fighters 98 and other oldies that I could stand to mention. So why should SSBB HAVE to have exploits/ATs/"hidden features" (whichever you wish to call them), in order to have a lasting gameplay? We should be hoping for a more balanced game that can stand the test of time, not for a new twist that can stand to change the game, in order to make it last.