I use opera mini and I love it. Just go to mini.opera.com through the regular browser and your BlackBerry will download the correct one over the air. You won't need to select a version or anything like that
BTW, I just wanted to point out that "QW" and "OP" keys control the menu for Opera Mini. Rolling the trackball horizontally will move the screen up one page and double clicking the * key will make the bars on the top and bottom of the screen disappear. After I found out those tricks, I had no complaints about Opera Mini