Main concern: Flex component is not good enough in user experience and functionality completeness, one example is TileList.
I do not agree Flex is the best option for building web application instead of AJAX. I will start blog a series in “doubt on Flex”, which I think Flex may be a rapid developing tool for developers, but it is a developer-oriented self fish tool, which sacrifice usability, web standard and make a lot of hurt to users.
If you said SWF is the best choice as presentation layer in web application, I am sorry I cannot agree, too. The biggest weakness of SWF is the text handling ability, which is never success than using HTML+CSS. Then I find Flex is weak in present image, too. I use TileList and itemRenderer to load external image, which is the common practice for every Flex developer, but I find that TileList reload everything on scrolling, if you try TagTV or pikeo, you will saw the problem, this problem has asked in Flexcoder list, but no solution yet.
If you check any HTML photo thumbnail list page, when you scroll down and scroll up, will you find the images had disappeared and need reload again? No! TileList is just an useless component in Flex.
Yes, Flex is just a tool favor developer themselves but sacrifice users.
Ely Greenfield from Adobe updated a post on how to make cache in Image Component in Flex framework hack, just like what HTML/CSS developer have to do CSS hack everyday?! They claim the extensibility of Flex framework is opened to developer. As I said before, developer have to put extra effect to solve the usability problem in Flex, because Adobe is provided you a just enought to use component, we, developer have to help Adobe to finish those what they claim is stable, robust framework to a usable quality?! That’s why they can provide an enhanced version of Flex builder and framework (they call it Flex3) but still target for Flash Player 9.