For years, the phrase â€PDAâ€phone combo†brought to mind clunky bricks that appealed to only the most connectivity-crazed early adopters. But the latest incarnations of these devices, now known by the more marketing-friendly tag â€smartphone,†are finally fit for the rest of us. So why do you want one?Beyond the obvious calling capabilities, smartphones keep your calendar and address book close at hand (and ever more easily synced with your PC), provide access to e-mail and the Web,