I currently use my Blackberry 9700 and iBluever on my ipad to tether using Bluetooth DUN.
I used to use MyWi 4.0 when I had an iphone 4, though it was good, just didn't like the steps required.
I had to open MyWi 4.0 app, then turn it on which took 5~7 secs, sometimes failed since AT&T's coverage sucks and felt like forever!
Then I had to worry about battery drain on my iphone and had to make sure I turned it off when I was done using it.
Now with my blackberry, I keep the bluetooth on all day without any issues of battery drain. All i do is open the ibluever app on my ipad and it connects instantly and off I go browsing the web.