1. When in doubt, file a bug.
Mac OS X and iPhone to some extent are a democracy, where bugs count as votes. Apple uses your bug filings to see which things should get fixed and which things should get implemented. I’d say at least half of the Q&A could be summed up by: “Please file a bug.”

At first it seems like the Apple Engineers are just passing the buck, but really what they’re saying is either:
a. “Yes that seems like a good idea, but I need you to file a bug so I can justify working on this, be it a bug or a new feature, to my manager.” or
b. “I’m not sure about that, but file a bug and if we get enough of those, we’ll work on it.”

BTW here’s how to file a bug in Apple’s Radar bug database.

2. Instruments is as important as Xcode and Interface Builder.
Every Mac and iPhone Developer is familiar with Xcode and Interface Builder. But Instruments is just as important, especially with the relatively limited hardware of the 1st gen/3G iPhone and 1st gen iPod Touch. There were a lot of good sessions that featured Instruments that are worth watching when the session videos come out.

Even on Mac OS X, profiling your application to improve its performance and memory usage is important to do with Instruments.

Another interesting tool to delve into is dtrace. Its the technology that underlies some of the instruments in Instruments.

Also I heard a new phrase “There’s an Instrument for that.” If you have access to the Snow Leopard betas (and you should get it via ADC), then check out the new ones that are available. If you don’t see one that fits your needs, you might consider filing a bug requesting it.

3. WWDC 2010 will hopefully occur in a bigger venue.
WWDC 2009 sold out the fastest as I’ve seen any (and perhaps the fastest ever?) 60% of attendees were new attendees. So there’s still another 3000 or so people who were at WWDC 2008 and previously that might have attended if they had purchased their tickets sooner. Add to that another 2000 or so developers that see the market growing due to the $99 iPhone and you’re over 10,000 developers that could be attending WWDC 2010. That’s roughly double the attendance.

OK I admit that I don’t really like lines and such, but the keynote line ran completely around the block back to the front! Moscone West was just overflowing with Mac and iPhone developers this year. I’m hoping that next year’s WWDC 2010 will be say in Moscone South or Moscone North. It might not be as cozy but it should give some breathing space and allow for more developers (including those who have longer purchasing cycles) to attend.

Wolf put up an official C4[2] t-shirt store.  It was a pretty interesting design but it didn’t have words so my wife was really confused as to where I got it.  She thought it was some sort of gardening thing.

Jose on the other hand, studied the t-shirt, analyzed the logic and found an optimization.  Gotta love the geekiness in that.

Now if I could only get old WWDC t-shirts too.  I left the 2008 one at the hotel and my other ones are getting worn out.

Update (Feb. 19, 2009): You can now buy The Wolf-Rentzsch t-shirt!  I was sitting right near bobtiki and josevazquez when they were making this shirt on the Southwest flight to C4[2].