The HDR capabilities of Photoshop have been limited. Most photographers interested in HDR migrated to third-party plug-ins, like Photomatix. Jay Kinghorn notes, much of the HDR fad hasn't been just to extend dynamic range but to also give photos a gritty, grungy effect. Photoshop CS5 has added HDR Toning and HDR Pro, whic greatly expand Photoshop's HDR capabilities. 

http://jaykinghorn.com/2010/05/06/30-days-of-cs5-hdr-pro-and-hdr-toning/