Does anyone have thoughts on using flash for facebook pages?
In my humble opinion using Flash in custom tabs on Facebook pages is not on optimal solution.
First of all it takes already quite some time for the content of an iframe in a page to load, so adding a plugin to that will only extend the time it takes for the page to load completely.
In addition to that you would need to do PHP or Javascript coding if you want the user to able to use social channels (like, post to wall) to interact with the custom tab content and integrating the existing Facebook plugins might be difficult.
Finally in terms of maintenance, a set of few good HTML templates with a small library of PHP and Javascript code snippets is all you need to build great custom tabs fast, without relying on an expensive and proprietary editor. Using Flash is simply not worth the hassle.
There is one domain thought where Flash is very popular on Facebook: social games. A lot of them are written in Action Script, and Flash makes it easy to develop these games pretty fast.