I just read a very informative article titled "Application of Fuel Cells to Fork Lift Trucks" in the September/October edition of Industrial Utility Vehicle. The article is posted on their web site (you should be able to find it with a google search).
The article is based on an analysis of fuel cells by Raymond. I felt it gave a rather honest assessment of the technology and where the ROI could be (though I've long ago learned to never trust the actual ROI numbers provided by an equipment manufacturer).