I see you've implemented the background loading of most aspects of a project, which is (conceptually) great!! However, while I know this version really is an 'in progress' version, it's unusable for me. IntelliJ won't stop eating my CPU. Especially when making changes to Pom's, IntelliJ will go to 100% CPU, and not respond anymore. Making changes to the pom's also has a lot of effect on the project structure: when making any kind of change (for example, the addition of a dependency), and even without saving, IntelliJ removes all the classes from view and starts processing the pom's, causing a high cpu load, which stops IntelliJ from responding. It's almost as if the background tasks (sometimes more than 20...) are running at a higher priority than the UI, which I find hard to believe.
On a small side note: I really don't like the new icon with the project options (scroll to/from source, flatten packages, etc!). The icons were much more intuitive and much easier to work with, since they are always there. Setting my correct settings for the project caused my twice as many clicks, since each click in the new version of intellij causes the project options popup to disappear, and, since the menu only contains text, I have to think more about which options I'm interested it. Thirdly, since the popup is text only, it doesn't have the visual appeal as the previous icons did.
I hope you can do something with my comments, if you need some CPU snapshots, I could try to create some.