I had the good luck to be able to try Confluence 4.3.2 at a collaborator's site and I will certainly not upgrade our installation from 3 to 4. The withdrawal of the Wiki editor (and with it the possibility to use an external editor) is a big blocker. I was hoping that the source editor plugin could be a compromise solution, but it's just like the RTE. "Copy/pasting back and forth between Confluence and your preferred desktop editor" as indicated in https://marketplace.atlassian.com/plugins/com.atlassian.confluence.plugins.editor.confluence-source-editor is really not a viable option for big pages. I need a simple form field which allows me to use a browser plugin to quickly transfer the contents between the form and my preferred external editor forth and back repeatedly.
Even better would be if you would support something like this https://wikitechcomm.onconfluence.com/display/CONF/Wiki+markup+toolbar+button which lets me edit at least simple pages in wiki syntax in my external editor. If you cannot/do not want to translate all your new XHTML features into wiki syntax and back, just give users a warning when a page contains features that cannot be translated, but let them work with wiki syntax when it's possible.