I've made a lot of posts about this topic in the past, in the WiiU subforum. My stance has always been that we need to wait until we either have a LOT more information on how these perform, or wait until the game comes out, for us to make any definitive judgments about custom moves.
My stance hasn't changed. We got more examples of how this is going to work at E3, but we haven't really seen it in action in a real match setting. We still know basically nothing, though a lot of my (pro-custom moves) assumptions have been proven correct thus far, like the number being not very high (12 moves per moveset, including the standard specials), most appearing to be very balanced in speed vs. power, etc. However, things like matchup theory, knockback, combo potential, techs, et all, are all still up in the air. The finer points need to be known.
A lot of the trepidation over the moves just comes from people's fear. Not everyone, mind you, but some people. Fear of the unknown, imagined fears of complications that aren't likely to arise (in my view), etc. What's the best antidote to fear? Truth. The more truth and facts we have on the subject, the more rational we can be.
I basically agree with everything @
Amazing Ampharos
has been saying in this thread. I think that, while there will undoubtedly -- undoubtedly -- be some tournaments that ban them, I can foresee plenty of times when they will be legal, especially as the game is just being discovered early on. Maybe we will find them very pleasant to use, maybe they suck. It remains to be seen.
Now, how deep does the rabbit hole go?
This "equipment" mechanic seems to mirror the Smash Run stats, only it operates under ratios and not buffing the stats up as much as possible. So if you raise speed, you lose attack power, and so on. This "equipment" feature may or may not be just as viable as the custom moves, but we know less about this than we do about the custom moves! It was literally just mentioned in passing during the closed-doors Q&A session with Sakurai, to a few journalists. We really need to wait and see how good or bad this is, but I have a feeling the "equipment" thing will not be as widely accepted, due to the very real possibility that there will be a greater NUMBER of possible "armor" pieces relative to each character, than with the custom moves (which is a constant 12 moves per moveset standard, as I suspected).
What about the figures?
The figurines are a separate system altogether. They're a whole other feature that, while they do incorporate custom moves, are not responsible for how the player plays the main game, i.e. VS matches with friends and rivals. The figures load up computer-controlled characters with custom stats and abilities, who duke it out with other CPU-controlled characters. There may be other nuances, but we will not be using the figures at conventional tournaments. This game mode is akin to the arcade games in Japan where you buy cards for bugs or dinosaurs, scan them into the arcade machine, and then watch them battle the CPU and "grow," the results being saved to your character's account.
It's essentially a totally separate game within Smash Bros.
Edit: The official website has further details on the "equippable items" feature:
http://www.smashbros.com/us/howto/entry2.html
It seems that there may be some merit to them, since they are likely controlled from the same submenu as the moves, however... I see a much greater increase to complexity, here. Like I said, there may be more than 12 of these per character. But let's say there's 12 armor pieces per character. The combinations of these armor attributes and the custom moves is a multiplicative number or results. The moves themselves are easily understood and researched, but the armor pieces are altering the more immaterial aspects of a character, such as their (possibly) speed, weight, launch resistance, knockback, power, etc. These are the kinds of changes that many, MANY people on this forum (myself included) are not keen on at all. It's just too technical. It cannot be mastered by a normal person. It's hard enough to balance a cast of, let's say, 45 characters or so, let alone a game where there are over 144 versions of each character. It's likely exponential, I'm just too bad at algebra to trust an exact calculation of mine.