I'm having the same problem - I'm trying to put a couple MB of text in a TextArea. It takes around 15 seconds before the UI becomes responsive again and then each keystroke inside the text area takes about a second to register. Have you made any progress on this problem? Have you given up?
The Flash text engine, and thus Flex in general, does not handle large amounts of text well.
Your best bet is to bring in part of the text at a time. You can read it all into an array perhaps, or maybe some other object, but don't put it all in the TextArea at once.
I don't think extending TextArea will help much, as the underlying text engine is the same.
Just read your comment to another flex user regarding slower performance from TextArea as the text files get bigger.
I am developing a word-processing application in Adobe AIR and am running into the same limitation, either in Flex 3 or Gumbo.
Could you detail your comment out a bit (or provide an example) regarding the use of arrays to render only those sections of text visible, instead of loading the entire text file?
In particular, how do you tie in what gets loaded from the array to the user's scrolling the text file up and down.
Thanks very much.