That is quite impressive. I wonder what percentage are new-to-Apple developers because of the iPhone, what percentage are long-time Mac developers who have never gone to a WWDC before, and what percentage are really non-developers willing to pay the large fee just to see the keynote?
Just thought I'd share that I'm a recent convert that is just starting to get into OSX development. It's funny because in the 15 years of using computers (I'm 24 now) I had never owned a Mac, except for a powerbook for a very short time. I remember when I was a little kid my Dad took me to a local reseller shop as we needed a new computer. We looked at the Macs they had that were at the time running "soft windows" or whatever, and TV tuners had just become a big fad. We almost ended up buying one, but my father just couldn't get himself to
"cross over to the dark side" , as he also had used PCs since the dark ages. (and no, he's a physician, not a geek.) So I grew up exclusively on DOS/Windows, only using Macs in junior-high and high-school --- I had sworn to never buy a Mac. Over the last 5 years or so, as I got more involved with web development and software development in california, I started to follow the progress of Macs up through the G5.
Fast forward a few years and I now spend an unhealthy amount of time following every post on multiple Apple rumor websites, not least because I have a decent long position in APPL. The next computer I buy will no doubt be the Nehalem Mac Pro and probably the 2nd generation of the Macbook Air (when it has an expresscard slot for 3G modem and USB3/Firewire 3200). I am also starting to become an OSX developer, and am very interested in experimenting with the iPhone.
I am confident that Apple will have an amazing next five years, and we'll see a fundamental shift in the broad computer and consumer electronics market, i.e., anything to do with servers/workstations/home PCs/laptops/ultra-portables/UMPCs/MIDs/cell-phone/etc. Apparently, I took less of a sip, and more of a chug of the kool-aid.

I know a lot of this is fairly obvious, but I think a big part of this shift that I've also seen in other Windows or Linux eco-system people has been caused by a few things:
1) Macs now use Intel processors. Suddenly, you could continue to use XP for development and for certain crucial apps (Visual Studio, etc) while learning to use OSX on the same machine.
2) Open source software and cross-platform development gained a lot of momentum, including Linux and BSD. You can now run all three major operating systems on one machine.
3) Windows XP lingered for years without any major update.
4) The disaster that is Windows Vista is released upon the world.
5) The iPhone is released, and every developer (and consumer) wants one. It highlights not only the incredible interface design of Apple, but also the strengths of OSX.
end result == More Apple customers and developers than ever, and a sold out WWDC. Also, my PC-stalwart father is going to buy an iPhone and a Macbook Air soon. I think Apple will do just fine over the coming years.
