The author of Learning Flex 3, Alaric Cole, has been working with Flash technologies since the introduction of ActionScript. But once Flex burst on the scene, he started focusing of Flex development. Recently Alaric put together a list of the top 10 things he thinks everyone should know about Flex. So whether you're considering using Flex for your personal site or business, read on to find out what Alaric thinks you should know.

Flex is the Look You Want The default look-and-feel of a Flex application is highly configurable. Due to the programmatic skinning at its core, a Flex application can be styled to your heart's content--changing colors here and there, modifying opacity, or changing the shape and size of the most common UI controls. And all of this can be done through standard CSS. Although, CSS is not a requirement, as MXML also allows one to modify styles and skins through simple markup. If you're using Flex Builder, you have an entire WYSIWYG editor for your application, allowing you to draw or plug in graphics and have all of the CSS written for you. In addition to this, there's a ton of themes for Flex applications, allowing you to change the entire look with a single line of MXML code.

It's worth noting that Flex, unlike Java or JavaScript, does not inherit the UI from the operating system in which it is run. That is to say, a Flex application running in Mac OSX will not have buttons that look like Mac buttons, and calling a Flex Alert box will not display a Mac alert sheet. Flex has its own look and feel built in--but if that operating-system look is one you're going for, there are a few themes available which can closely mimic this.

Flex is Light, and Fast
Built on ActionScript 3, the Flex framework is surprisingly speedy. Initialization times have been improved dramatically over ActionScript 2, and built-in support for lazy instantiation helps a great deal. Using a new JIT (Just-in-Time) compiler, your code runs blazingly fast. Rich data visualization and advanced animations are entirely possible without hogging the user's CPU. While lots of 3D animations have been the bottleneck in the past, new support in Flash 10 may help. There's even hardware acceleration for video, to take advantage of modern graphics processing cards.

Although some will argue otherwise, Flex is light, as well. While using a set of UI components will definitely be larger than made-from-scratch ActionScript coding, the components are small considering how powerful they are. In fact, a typical application built using an AJAX framework can oftentimes run larger than a similar Flex application. The Flash Player itself is a download of a few megabytes, though it's often pre-installed on computers. It's also worth mentioning a new feature, called framework caching, can shave off a good part of the download for the framework components. This feature can store the standard Flex UI components on the user's machine so that other Flex applications will load instantly, without the overhead of downloading the entire framework. This can allow advanced applications that run under 100kb.

Read the rest of Alaric's Top 10 list here.