Ok needed to help with some performance testing of our ADF apps login process and struggled a bit with some of the stuff so here are my findings:
Firefox and Tamper Data: https://addons.mozilla.org/en-US/firefox/addon/tamper-data/
So so handy for catching all your post and get parameters cookies and headers. A must for automated testing to see what is going on in your app. More of a diagnostic tool.
Really really cool once I had found Chris Muirs post on setting up jmeter for ADF. (link below).
You can make complicated test cases here very easily and run them any number of times in the ide.
Very handy for doing volume testing.
If you want something that will record what you are doing/ click in your browser and export your scripts to JMeter for automated testing this is the tool for you.
Holy moly this is so easy to use and test with - just fire up firefox start the selenium ide add on and start recording - everything just WORKS. You can export this to junit tests and watch as all the magic happens. Really really cool.
Also dont try anything fancy with the login just use j_username and j_password posting to j_security_check. See attached script. http://dl.dropbox.com/u/63575405/Script.jmx
I like the selenium using unit tests for most of my stuff but I find jmeter incredibly handy for quick perfomance testing.