1. These players have only been playing for 2 days, but remember that the invitational players had only played the game for a few HOURS. The CT videos already show what a big difference a little practice makes, as they are already moving faster and with more confidence than the invitational players, and at least attempting (even if failing) to follow up their actions with other things. This shows that the game is capable of moving pretty fast, and any preliminary fears of "Brawlness" from the invitational can be attributed to player inexperience and basically not being able to show off the full potential of the game.
2. The videos with the Nintendo rep's ZSS show a huge contrast to the playstyle shown by Zero in the grand finals match. This guy was going on the offensive a lot more and even pulling off some short combos. This is evidence that the game does not have to be played only by camping, and that what we saw can be blamed on Zero's experience coming from a Brawl background and not on Smash 4 itself. (Also, shoutouts to that rep for being super chill and joining in with them.)
3. As if people needed any more reminders that this game is literally an unfinished prototype, Pikachu floats in the air for about a second after his Final Smash ends and before he falls to the ground. I observed this in videos from both E3 and Best Buy. It's not like the game will be shipping to disc in its current form, guys.
4. The landing lag issue seems like it's been the #1 biggest complaint that people left as feedback with Nintendo reps (from all the posts I've read of people who said they left feedback after the demo, almost everybody mentioned this). If Sakurai is actually going to take anything from the demo to heart, at least this thing will be at the very top of the list.
5. The other biggest problem that stands out to me as a spectator is that the blast zones are all too far out. Obviously a lot of stages themselves are really big, which is a whole separate issue that we may have to deal with later, but even on Battlefield and Smashville, characters can fly out really far without dying. I would like it if they literally just moved the blast zones closer to the stage.
Overall, aside from points 4 and 5 on my list, these 1v1 videos are one of the best things about Smash 4 to come out of E3, and they should be taken as nothing but positive for the game, especially for people who were skeptical after watching the invitational.