Pure Cross-browser application are targeting desktop like interfaces. However, performance improvements is radical in the XUL version of an application. This is why OneTeam offer a desktop-like feeling.
Performance of the pure cross-browser Ajax applications, cannot match the feeling of a true native set of widgets. This is why we bet on XUL for our OneTeam enterprise instant messaging client. With this approach you have a full web application with zero deployment, that can really be as responsive as a desktop app.
For the sceptical, read this article from O’Reilly: XUL-Enhanced Web Apps (better read from Firefox to compare the examples). The rendering speed for a large three is 4400 ms in DHTML versus 650 ms in XUL. Yes, it makes a real difference in term of usability.
You can check it by yourself in OneTeam. The beta test for our XUL based Enterprise Instant Messaging has started and the demand is huge. Please be patient, we are creating new accounts every day.