Upgrading did nothing to solve the problem (we've had 6.0 running in a development build for quite some time now) and additionally created new problems that had to be solved on our end for the latest version of our product in development.
This is in reference to 6.0
If I type text and click save it does not update. If I click outside of the editor after I type text and change focus then click save it works. If I type text, click outside the editor to change focus, click back in type some text only the first set of text I typed will get save off.
For code that is "totally rewritten" it sure seems to be acting in the same exact way the 5.3 version did like I previously documented and experienced.
UPDATE:
I've found the problem with Cute Editor. However you handle updating the value of the text is in my opinion quite poor and is exactly the same for 5.3 and 6.0. I can replicate it over and over and control it. In order for the value to be properly updated there seems to be a need for an onblur/onchange event to fire. The problem with this is that clicking our save/submit button does not allow this to happen in IE. This would explain why I thought getHTML worked from the address bar, since the onchange/onblur or whatever event you are using gets fired off properly.