Well, I will just point out some basics before anyone else does. These are assuming a BES, or Blackberry Enterprise Server, in place.
-Wireless, Instant Synchronization of Emails, Contacts, Calendar Events, Tasks and Notes.
-One Handheld used for the above, as well as Voice Calling.
-IT Policies allow for added security, easier maintenance, and call/sms/email logging.
-Application Push to handhelds allow a companies custom apps to be used for mobile employees.
-Ability to view word/pdf doc's on handheld.
-Tons more that I'm forgetting
-Expensive equipment, data plans, and software (some, not all)
-Addictive (yes, they are. trust me
-As in all software/hardware, problems can arise day or night, weekday or weekend, leaving mobile employees out of email contact (doesn't effect phone).
-It's a leash. If you have a Blackberry, your customers know you received that email.
-If the handheld is lost or stolen, data can be sacrificed without the proper security/procedures in place.
I have to say, having a BB (by choice, not obligation) has made my work life much easier. Monday's are no longer a surprise of coming in and seeing 100 emails from other employees about 'urgent matters'. My favorite feature in BES is the IT Policy. One example, my fiance's company hired an Office Manager, and she was a no-show, no-call one day (a very important day). She called the next morning and quit, and refused to come back to the office. Rather than wait for her to mail the Blackberry in, and wonder what she was doing with the sensitive data on the handheld, IT was able to immediately lock the handheld, change the password, and deactivate it in a short time, rendering it useless. They never got the handheld back, but at least they know she had NO access to their data, and couldn't rack up a bunch of charges.
Point of the story, BB's aren't just that 'cool' flashy thing to have. It's almost everything you need to work, without being physically at the office.