Google has put some effort into making their online office suite compatible with iOS devices. Most of the work was focused to enable reading your documents on mobile devices. The ability to edit an online doc on the iPad and the iPhone has been possible for a couple weeks now.
Today Google has revamped their Google Docs mobile interface, making it very close to the desktop version.
Google’s desktop version is preferred for more complicated document editing like font, alignment changes, editing spreadsheets, and formulas.
For general use of Google Docs it is recommended to use the newly revamped mobile version, which can be done easily from your iPad with just a tap to switch to the mobile version.