Recently I have seen a lot web apps use Adobe Flex to develop a rich UI. I had last looked at Flex when it was in its infancy. At the time it was pre beta and Flex was being positioned as a tool to build 3-D environments. I played with it some, but I didn’t quite see the potential outside of certain niche development.

Flash forward a few years and Flex is now making us all think twice about the AJAX/CSS/DHTML model for rich Internet applications. I designed and deployed a project for a Fortune 500 company one year ago that made heavy use of a rich UI. We mostly used the script.aculo.us library for our visual effects along with some home grown components. In the end we got most everything working as we wanted, but had to cut and run on some features because of time constraints. The real pain point in developing all this was the endless issues of cross browser support. As expected it all worked in Firefox, but maintaining compatibility between IE 6 and IE 7 reached nightmarish proportions.

We are now at the point of doing some refactoring of our code and I am looking to replace some of our UI features with Flex. There will certainly be a learning curve, but appeal of not having to rely on countless CSS hacks and wasting precious time on tedious cross browser issues is very appealing. Below is a list of pros and cons to Flex versus the AJAX/CSS/DHTML way of UI development.

Pros

Flash plugin has over 98% penetration in the US market (I’m not sure about international figures)
No more cross browsers problems
RIA can be taken to a desktop app or widget much easier
Single framework with a solid standardized IDE
Full vendor support

Cons

Less people with Flex experience
Less open source code and off the self components
Less examples found on the net
You are now tied to a single vendor
Possible SEO implications