Nope. i registered my interest online, like wat u have said. Was hoping for them to get back to me anytime. So i just waited and waited. Finally, they sent an email to me (found it in my SPAM mail). They have a link inside for u to make online purchase. You will only be able to purchase the 1 u showed ur interest in. Which means if i showed interest in White 16GB, i only can choose this. If i choose another, i wont be allowed to do it.
I didn't expect them to get back to me so soon (3 weeks) but well it was pretty fast i guess.. Hope u will get ur iPhone 3GS soon too...