I've been a loyal BlackBerry user since 2004. Since then, I've had six of them (see photo below). I finally made the decision to switch over to the iPhone 4s this month. The iPhone is a significantly superior product. The operating system is much slicker and the apps are phenomenal.
Apple's App Store took the PDA marketplace to a place that RIM never imagined it would go. As evidence of this, the last BlackBerry I bought didn't even come with the BlackBerry app store installed. You had to go out to the web and do a tedious installation process to start buying apps.
All of that said, I'm one of the few that believes BlackBerry is here to stay (though it may require an acquisition by a larger player). The new BlackBerrys are superior devices for corporate users and more and employees are requiring a mobile device for work. And the lack of a keyboard puts the iPhone at a nearly insurmountable disadvantage as an email device (email is the most used app for corporate users).
I don't think it's implausible that most corporate users will have a work device (BlackBerry) and a personal device (iPhone or Android); just as most corporate users have a work computer (very often a PC) and a personal computer (very often an Apple).
Regardless, BlackBerry is up for a big fight. And it'll be an interesting one to watch.