You have read about using IntelliJ as an XML editor on this blog before, and I would like to share a tip with those of you who are now using IntelliJ1.
Yes, I do like IntelliJ, but I have to admit that it comes with its own set annoyances. In particular, when alt-tabbing from another application to IntelliJ, it used to just freeze on me for a few seconds. And that happens a lot with web development, say, switching back and forth between IntelliJ where you are editing a CSS file and IE which more stubborn than a mule and more dumb than a donkey still doesn't render that page the way you want2.
The solution is pretty simple: give IntelliJ more memory. You can do this by editing the bin/idea.exe.vmoptions (on Windows) file, which you can find in the directory where IntelliJ is installed. It looks like setting the maximum heap size to 256 MB is enough for the projects I am working on, but your mileage may vary. Also, as I do for the VM running Tomcat and Orbeon PresentationServer, I set -Xms and -Xmx to the same value.
1 If you are wondering what people think about IntelliJ, try to Google "xml editor intellij". While Google doesn't quite have the answer to everything just yet, the first link in the search results points to a page titled "Best XML Editor" on the JetBrain site. The next link is titled "Whacky XML editor in IntelliJ IDEA" and points to a post in the xml-dev list. Then come 2 links to the same post, but on the sites of 2 other companies doing XML editors: StylusStudio and <oXygen/>.
2 Hoping that the newly released IE 7 will solve your problems is pure illusion.
One thing you don't mention is that you can also turn off file synchronization upon frame activation. This can take a really long time if you have a large project. You turn if off under IDE Settings -> General.