Google claims more than 100,000 small to medium enterprises have replaced Microsoft Office with Google Apps, along with big names such as GE, Procter & Gamble, Prudential and Loreal. These big companies are paying for the Premier Edition of Google Apps, which promises 99.9 per cent uptime - the equivalent of being down for a total of almost nine hours in a year. Still, Google can't make that promise for your ISP and your office network. If they both offer 99.9 as well then suddenly your overall downtime has blown out to more than a day - more if your ISP can't even offer that level of reliability.

Google Apps is a great idea, but it's crying out for a way to synchronise documents between the online storage space and your desktop. This would mean you've automatically got the latest versions wherever you go, but a backup to call upon if your access is down.

If Google Apps was integrated into a desktop suite such as OpenOffice - so you could edit files on your desktop but know the latest version was stored online if you needed to access it on the road - then Microsoft would really have something to worry about. Google is rumoured to be considering buying ThinkFree, one of the most tightly integrated Office-like online suites. ThinkFree also offers a desktop-based Java version and a premium service is under development that synchronises documents in the desktop and online versions. Acquiring ThinkFree now looks less likely, but with Google you just never know.

Sure it goes against the whole Web 2.0 philosophy, but until Google Apps incorporates an offline option then it's only preaching to the converted. It's going to struggle to win converts amongst old school Microsoft desktop users who still don't have reliable enough internet access to trust their documents to Google Apps.

Microsoft Office is Microsoft's cash cow, so Google Apps has the potential to really hit Redmond where it hurts. Making Google Apps documents available offline could finally create a true "Office killer".{moscomment}