I like flip phones because I like having the controls hidden, so I don't accidentally answer calls in my pocket if I forget to lock it, or have to hit soft unlocking keys when I want to place a call. They also protect the screen better, and tend to have better acoustics. They also often have better ergonomics - I have more than a touch of carpal tunnel / weak hand muscles, and it somehow helps to have a phone that, when open, is not as dense as a candybar/slab phone and is well balanced around the hinge.

That being said, I do want an iPhone, Treo, or Blackberry in the next couple of years, and so far, no good flip phone options there -- I might want to give this Blackberry a look.