(With apologies to MIB)
It's small, charges via USB, has a decent browser, a killer UI (spartan and low on eyecandy, but extremely efficient), a well-rounded internal software suite that includes all the usual PIM features plus Blackberry Maps - which I wrote about earlier - and a number of great freely available J2ME/MIDP applications (you can install Opera/Mini, Google/Talk, Google/Maps, etc.).
It has also been keeping my life together via seamless syncing with my corporate Exchange server (there's Mac syncing software freely available, and I redirect my .Mac account to it), and it now sports a "nearly good enough" camera (i.e., a decent fixed-focus camera with a relatively sharp sensor). And, in a pinch, it has doubled both as a GPRS Bluetooth modem and an USB storage device (and yes, you can encrypt the memory card).
For someone like me (who is online at all times, socially if not professionally), it marks the defining moment when an ordinarily-sized phone was truly empowering.
Like the local slogan says, information is power - and there's no better way to wield it on the move right now.