Hi,
I use this film regularly, most of my recent B&W shots (think of 35mm cameras; in MF I pefer more traditional ones like FP4, APX or Fortepan) was XP2s. I'd say that XP2 is a very special film. As others mentioned, it has probably the widest exposure latitude of all films available today, and even the very special "balancing" B&W developing methods (think Dulovits) are just a bit better, at the cost of using some hard to get, expensive and extremely dangerous chemicals and extremely low ISO ratings. The resulting negs are of course of extremely low contrast, but they have all the detail in the highlights and shadows that other films would have already cut. The hard thing is to make decent prints or scans from this, as most of the time you will have to heavily raise contrast (and to make the final decision on what to expose correctly) in the darkroom and/or during digital post-processing. Most "analog" labs or automated digital processors will fail here for sure, but careful handling can achieve exceptional results. Using high contrast and/or multigrade papers is a good point to start. For the scanning people, a "brave" use of a "Levels" tool in PS is absolutely necessary before anything could be published or printed. Gabor