There are a lot of people out there trying to compete to be your front-end Ajax/ web 2.0 framework of choice.
In the midst of technical framework comparisons, ask yourself, "Where is the RIA Industry Going?"
We feel the future of RIA's is the 'Next Plateau' where frameworks are absorbed into IDE's and online content management tools.
Web 2.0 UI toolsets are falling into two major categories:
1. Visual Effect frameworks - transition effects for content display
2. Application Frameworks - layout management and ever growing widget libraries
3. Data Visualizations - charts, graphs, etc
Prototype and Scriptaculous lost the early mover advantage by not focusing on good documentation. After all, how good is a framework if the learning curve is too steep?
Extjs came out running, building on top of the YUI framework and focusing on documentation and performance benchmarks first, then licensing, training, and, consulting. A more than cozy relationship to Adobe, and now the addition of GWT support means, [wink wink], looks like someone's positioning to get bought.
We wouldn't be surprised at all if Adobe bought Extjs, given all the integration work Jack's done with their AIR framework and Adobe's eagerness to get yet another generation of web designers coding javascript without any clue as to what is going on under the covers.
Even as frameworks mature and learning curves lessen with more 'out of the box' features, non technical users will continue to prefer a tool to wire things together for them.
