There are two big problems with online applications. One is a limited UI - you do not have the rich controls and interoperability that you do with desktop applications. The other is connectivity - you need an internet connection, and given there's no connectivity on the Tube or most flights this can make many applications useless during such periods of time. Google have today gone someway towards solving the latter with Gears.

Gears offers two things that previously you'd have been looking at something like Apollo or Silverlight to provide - threading (rather than a single JS thread) and offline data storage. Hence appropriately enabled application, like the new version of Google Reader, can be toggled into an offline mode and used in the absence of connectivity. Also, Gears is really cross-platform and cross-browser, with IE, Firefox, Safari and Opera support promised, and it works very nicely on my Linux box at work (unlike Silverlight).

It also fires a salvo in the direction of Microsoft, clearly stating Google's desire to provide an application platform that threatens their core business. Further, once Google Docs is enabled it suddenly becomes rather a greater threat. Interesting times.

Now if they'd only release a synchronisation API for Reader I'd be chuffed silly. While Reader is a superb, quite possibly the best, web feed reader, it doesn't yet match up to NetNewsWire. Unfortunately that leaves me stuck using NewsGator as a synchronisation server, which has a rubbish web interface and no client whatsoever for Linux.