This is something I wanted to comment on as soon as the Big Three's conferences were over, but I opted to wait just in case there would be another surprise waiting later at the Expo and so I would be sure I'd have an informed opinion.
Now that all the hoopla is over, on to my main gripe with the E3 experience.

First up to bat was Microsoft, and boy did they initially impress. Yeah, "initially" seems out-of-place in that sentence, but that's just why I put it there. Natal sounds great on paper and could bring lots of new possibilities to the table, but when I started to think about it and watched the conference after the fact, a bitter taste was left in my mouth. In order to better illustrate this, let me give you the short version of what went through my mind as I watched the conference:

MS: Hey, we at Microsoft have decided to go beyond just the wiggle-waggle that the Wii offers and have a peripheral that can detect all sorts of body motion!
J: Neat! Let's see what they have to show!
MS: Watch me as I do broad gestures in order to clumsily throw paint on a wall!
J: Okay. So we just went from wrist-waggle to arm-waggle to get a poor response? It's only a tech demo; surely, they'll have something good later on.
MS: And here's Peter Molyneux!
J: Oh sweet Jeebus, not him...
PM: Hey, I can interact with this pre-programmed AI!
J: That's not interaction, asshat; it's theatre. Just go away now. What about real games from real developpers?
MS: Let's give Milo a round of applause! [J: No.] As you can imagine, Project Natal will revolutionize gaming as we know it.
J: When does it come out?
MS: Eventually.
J: And how much will it cost?
MS: Whatever is written on the price tag.
J: What about games?
MS: We'll see in due time!

I know that I grossly exaggerated, so don't hold it against me. However, it is how I feel regarding the whole thing. There are many potential problems with the thing that have been explored already, and the "Visions" video is so ideal that, obviously, acheiving that amount of realism will be impossible.
What about the non-existent lineup (seriously, you just announced a slew of new titles and couldn't get even one of them to run on the damn thing?) and info? (Price? Date?) How am I supposed to get excited about something when I have next to no information about it? The whole thing feels like a smoke-and-mirrors trick to me.

Let me skip ahead to Sony. They had a much better presentation than Microsoft - Molyneux wasn't there, so that gives them a few points. Their tech demo worked: it proved what it had to and, for all intents and purposes, it worked very well.
A few question arose, though: Do I really need the camera? Are two motion controllers necessary? And last, but not least: What advantage does this have over WiiMotion+?
That last point remains a mystery to me, as I simply cannot figure it out; especially considering that the camera probably is needed for this to work. What happens when it loses sight of the cameras? Does the game spaz out like that Natal Avatar?
I can't say that I have much to complain about Sony's offering, though. They showed that it worked, and that's already a huge step. Unfortunately, just like Microsoft before them, they have no date, price nor games to go with the hardware. Nothing more than a meager tech demo. Again, I felt disappointed.

Allow me a slight digression here, although it is related to the matter at hand. Microsoft. Sony. I don't think you two could have picked a more awkward time to present your projects.
Nintendo unveiled their motion controller 3 years ago and just now you think it might be a good idea? The Big N is not only demoing, but also releasing their upgrade to the initial motion controller in the very same week! With games that work with it, no less! It could be argued that Nintendo just released Wii 1.5 with their WiiMotion+, and after 3 years, all you have to show are tech demoes, without software, release schedule or price? You have to be kidding me! You're way too late to this game.
Not only are you too late, one could argue it's too early at the same time. Your hardware is shown three years into the current life cycle of video game consoles - four, in the case of Microsoft. Instead of waiting to pair that technology with a new console - one which would revolve around it - you opt to have it as an add-on. This gives me the impression that you're not commited to your projects. It's like if it succeeds, then it's all for the better; but if it fails, then it's no big deal.
Of course, that last point may be proven wrong in the future, but I get the feeling that with your current attitudes toward motion gaming, your projects are destined to be forgotten.

With that out of the way, let's talk about Nintendo. Yeah. They... uh... what? Out of all the announcements made during their conference and the expo, the Wii Vitality Sensor is the biggest question mark.
Iwata walks on stage, a picture of an attachment - with no bypass for a Nunchuk - appears on screen and Iwata explains that this little gadget can measure your pulse and skin conductivity. He talks about learning to relax with the thing and walks off. The only thing missing was an announcer saying: "Now, back to our regularly scheduled program."
Everybody was left dumbfounded. Okay, so you got something. It could be cool, but you barely share a single idea with us and leave the rest to our imagination.
It's not that the perpheral has no potential to be amazing, but I'm not seeing it. This isn't the characteristic Nintendo I've come to know. Usually, when they debut some new hardware or accessory, they have something to show for it.
"We built this motion-sensing controller! Try out all sorts of stuff on the showfloor!"
"Miyamoto came up with the idea of a balance board! You'll find demoes in our booth!"
"You can now upgrade the Wii Remote's capabilities using this little device! Check it out before you leave!"
"We have a vitality sensor! Later!"
As the days go by, I try to read more into it than just the announcement of an accessory. Is it a glimpse of what's to come? Are they just experimenting, like at the end of the Gamecube's life? Is it something to warn their competitors; that as soon as they release their stuff, Nintendo will immediately counter-attack with a new card and make them seem behind the times?
I don't know the answer. Only the higher-ups at Nintendo do. I do, however, beleive that the last option is very probable. We'll have to wait and see.

In conclusion, all the new stuff that was shown at E3 was disappointing, because it raised more questions than it really answered. I say "disappointing," but that's only for the time being. I really hope I'll be proven wrong.

Anybody else have similar thoughts out there?