Breath
Unlike Gears,Adobe AIR doesn't require a browser to exists. Adobe AIR can do everything Gears can do and more. Air is not just about building offline/online apps ("occasionaly connected apps") . Air is about building desktop apps. You can build apps that never connects to the internet in AIR.
Google gears is not a runtime. It requires a browser to survive. AIR is a runtime own its own (almost like Java runtime, if you need anything to compare to). Air apps can be built just using html/javascript. Flash is not required. If you want, you can use flash too .
AIR allows traditional web developers to migrate to desktop development without learning C or Java or VB or whatever. In short AIR allows web developers to build complete desktop apps like Winamp,iCal,Paint etc.that doesnt require a browser/internet connection to exist.
In short, comparing Adobe AIR and Google gears (and hence Google chrome's threat to AIR's existence) doesn't make any sense at all.
Flash is THE best way to deliver heavy weight rich internet applications on web.
With Javascript, you would:
if(ie 5){ //do stuff.. }else if(ie 6){ //do stuff.. }else if(ie 7){ //do stuff.. }else if (IE generic fail edition){ //do stuff.. }else if(Opera){ //do stuff.. }else if(Safari){ //do stuff.. }else { // do stuff }
With Flash you would just "do stuff"..
Now, this doesnt mean Flash is better than Javascript.But when delivering heavy weight RIAs, its better to stick on to Flash.Why overload client side with untargeted code?