eBay has an AIR app for managing your eBay activity. Launched during MAX 2007, even though it has been around since last year’s MAX. They learned things from it.

First, recognize that desktop apps have much more power than a web app. Why doesn’t everyone do them then? Desktop apps are a lot more expensive to build! Web apps have been getting more expensive as standards of quality rise, but they’re still cheaper than full-fledged desktop apps.

eBay built a fully-functioning prototype in just 3 months. Here are some lessons learned.

1. Start with a good foundation. They started the AIR app because they had already been building web services and API for eBay. So all they really had to do is build a UI. All the web service hype from 2002 was indeed hype, but now, five years later, the concept is finally coming together in a very key and important way. These web services are a great way to connect desktop apps to the web. Store your business logic in the web services that the desktop apps can access.

2. Design takes a long time. Of the first 3 months, six weeks were spent on design alone. Why? (a) AIR offers a lot of freedom. If it was more restrictive, it would have been more straightforward. (b) They were pioneering things. There is not a prescribed manner to address a lot of the questions that come up. (c) Expectations have been raised for user experience.

3. Betas are really useful. I mean real betas, not marketing betas. They have thousands of users in the beta program and they get tons of feedback.

4. The most important AIR feature is… Freedom from constraints of the browser. No frustrating back button. No location bar.

5. Users don’t care about software platforms. A good platform, like AIR, just gets out of the way. Installation, auto software update, startup,  etc. Beta users haven’t complained about these kinds of things–the kinds of things that typically hinder Java apps or some other platforms.