To skeptics, Office for the iPad is arriving dangerously late. That’s because the delay has given people who use iPads, especially business professionals, years to get used to using the tablet without Office, a suite of programs that includes Word, Excel and PowerPoint. Start-ups like Evernote, Quip, Smartsheet and Haiku Deck, along with Apple’s own iWork suite of applications, have filled the void left by Microsoft with productivity applications that work on tablets and other devices.