This blog reported in September, and again in November, that Apple and AT&T were facing a flurry of proposed class action lawsuits regarding the performance of the iPhone 3G on AT&T's higher speed network. On November 26, 2008, plaintiff James Pittman sued Apple for varrious product defects. (Jim Dalrymple, Apple Faces Another 3G Speed Lawsuit (December 4, 2008) www.pcworld.com.)
My iPhone seems to do as well as any other cell phone at holding calls, which is to say that it is passable at that task. The 3G speed is substantially better than Edge, and I get 3G in a significant portion of the Los Angeles area. Just my experience.