I have a Mac Pro, a MacBook Pro, an iPod Touch, and a Blackberry Curve. None of those things will do what I expect that an iPad will, so I'm waiting on FedEx to deliver my 64 gig 3G.
I own a rather ancient BB 8830 and every time I sync I get duplicates. An iPad will do nothing to make this situation better (or worse) so having a BB doesn't affect my decision to buy an iPad. I also own an iPod Touch. I have an iPad 16 gig reserved for pickup on April 3rd but haven't quite decided whether I intend to show up or not...
I have an iMac, Windoze based netbook and iPhone but still getting an iPad.
Even though I've never had any interest in getting a Crackberry, if I did own the devices you mentioned, I'd still get an iPad
blackberry was the worst. i had lost my iphone, and got a blackberry in the meantime. i had it for a month and hated it!! so much! im so glad i got my iphone backk ahhh.