Though we can't tell you what day during April, Quickoffice has announced their Office suite for iPhone, will be available sometime in early April 2009. QuickOffice for the iPhone can display, edit and create MS Word and Excel documents. It also has viewers for iWork files and PDFs (the iPhone has a native PDF viewer anyhow). It includes such nifty features as cut/copy/paste for Word docs, landscape view with access to the easier to use landscape iPhone keyboard, MobileMe file access and WiFi transfer of files to and from the desktop.
It will sell for $19.99, or you can get QuickWord for $12.99 and QuickSheet for $12.99. Sorry, there's no PowerPoint support.