I'm going, went last year for the first time. It's a great dork-fest! Here's my 2 cents:

1. I didn't attend hardly any of the demo theaters last year, so I'm planning on hitting those more this year
2. The EXPO is only open on Monday, so if you want to check out the vendors, you gotta do it on Monday
3. Don't be shy - if you are walking through the ESRI showcase and you see a ESRI staff member that gave a talk of interest to you and/or you have questions, grab them and talk to them, that's what they are there for.
4. DO NOT miss the party on Thursday night, last year was a blast
5. If you like burgers, you MUST go to Tylers - only open for lunch and cash only