I must be missing out bad. ~_~
I feel like going next year. I plan on going to Tokyo twice in 2013.
These shows stopped doing it for me long ago... even when I was still well enthralled with even current games. Well, some of them. Now, it's just crowds of sweaty otaku, socially awkward people, and D-list wannabe models dressed up in stupid outfits that probably have no idea what waxing their pussy is all about. I can ride the Yamanote from Shinjuku to Harajuku and walk down Takeshita Doori and get ALL of that... on any Tuesday it's not raining.
I was able to attend in 2010 as press on one of the trade days. I had to show a business card, photo ID, and a letter of assignment (I was a freelance writer).
The longest I had to wait for ANYTHING at the show was 15, maybe 20 minutes. And that was for the PS Move. I didn't bother waiting for that.
It should be obvious, but people planning to attend need to realize it's a Japanese show. This could hinder your enjoyment of the show. It was rare I found any game that was English. The Behemoth--the guys behind Castle Crashers and Alien Hominid--had an English-language demo of their new game up. Everything else I saw on the floor was Japanese. Capcom's suite at a nearby hotel did have English-language demos available, such as Okamiden, Mega Man Universe (RIP...) and some others, but that was invite only.
But being able to walk around and not really wait long to try something was very nice. It made the show almost relaxing.
Now, if you want to see all the cosplayers and chaos that goes on, then by all means go on a public day. But to reiterate what others have said, you've been warned. Here are some photos of what you can expect on a public day (not my photos):