Most power have been disappointed with the performance of Rich Internet Applications (RIAs) based on Asynchronous JavaScript with XML, or AJAX, according to a new research report from Forrester Research.

As a result of the AJAX limitations, the research firm recommended that business users consider emerging next-generation RIA technologies like Adobe AIR from Adobe and Microsoft's Silverlight toolset.

According to the report, which was released late last week, power users find that AJAX applications are very complex and their reaction time is limited. The reaction time and general speed of user interaction is always limited with AJAX business applications, the report said.

"The local rendering of complex business screens requires serious client CPU time," the report noted. "A European retailer that wanted to migrate screens from a Visual Basic rich client to AJAX reported initial load times for complex screens of many seconds. Given the nearly instantaneous display of the old client app, this was annoying for power users."

In addition, because most AJAX frameworks tended to keep all real business logic on the server as opposed to local systems, user interactions might require a roundtrip communication between the browser and server for each input field. Some large applications could easily have 50 fields on a single screen.

As a result, AJAX developers told Forrester that they had to reduce real-time input validation compared with traditional rich clients to meet performance requirements. Real time input validation is a top priority for power users, the report said.

Forrester said that as AJAX framework vendors worked hard to overcome these barriers, they had encountered additional problems. For example, improvements in bandwidth had not led to expected AJAX performance gains.

"Bandwidth has widely improved and people are starting to realise that many AJAX applications have not speeded up accordingly," Forrester noted.

In addition, most corporate desktops ran a virus scanner that investigated each line of JavaScript, which slowed the rending performance of the browser, the report noted.

The problems likely could be overcome if AJAX vendors and browser companies moved in the same direction to fix them, but Forrester noted that the opposite is actually true. Microsoft was investing in AJAX alternatives like Silverlight while Mozilla lacked the "hundreds" of developers it would need to fix the problems. Meanwhile, Apple's Safari has not been widely adopted for a software vendor to rely on it as the browser of choice.

"You might have to implement some business logic twice - in the client AJAX framework and in server-side transactions," the report said. "And while browsers might become faster, you should plan to test for both Internet Explorer 7 and Internet Explorer 8 until Internet Explorer 8 becomes mainstream."

For the study, Forrester studied three types of AJAX applications that are replacing traditional client applications: AJAX-driven mash-ups, a gradual re-factoring of an HTML page using AJAX and using AJAX to completely replace an enterprise application.