Hi Paul (nice to see you again)
I've had a company issued Blackberry for almost 2 years now, and it's through IM Cingular.
the range of coverage is nationwide. When I was on vacation in New Mexico last year - I was still able to receive e-mails that were routing through my company's Exchange Server in NYC. (Which was an interesting way to observe the effects of the blackout...)
It IS "always on!" If someone sends you something at 3:00 in the morning - it is automatically "pushed" from the e-mail server to your Blackberry. There are ways to manage this... There is a power button, so you CAN turn the damn thing off (lol) and there is also an "Antenna" button, so you can turn the WIRELESS part of the device off! Very handy for Airports, Cardiac Units, etc.... If you DO choose to use the rest of the device as your PDA, this means that you can be productive, even if you are not capable of receiving e-mails/phone messages for a period of time.
The Blackberry CAN handle attachments, graphics etc... (this is a FINE LINE I'm going to draw) I receive PDF's and other types of large Graphic files all the time, and no matter where I am I can FWD them from the Blackberry to the appropriate team members.
You CANNOT VIEW the files on the Blackberry though!
Also - one other important point... you can set up the Blackberry a variety of ways... you can use it to automatically "push" e-mail to you from your current e-mail box; or you can set it up so that it only receives messages sent to it's pager address - which is a unique & seperate addreess assigned to it when you purchase the Blackberry.
Now that I've said all of that.....
I've had mine for almost two years. After two years, my MAIN Productivity TOOL is STILL my Palm m515. The Palm is simply a more elegant, user friendly, more powerful device than the Blackberry. The Blackberry PIM software is really worse than the first version of the Palm OS from 1987.
There are a TON of things that I can do on my Palm that I can NOT DO on the Blackberry, and I don't want to give up that functionality. So, I am resigning myself to carrying two "wood blocks" now
Hope that you find what works BEST for you!