I have experienced exactly the same. Xcode 4.4 crashes regardless of project or code. It crashed in OS X Lion 10.7, so I upgraded to Mountain Lion 10.8 and it still crashes when I run and build with a target of iOS simulator.
It looks as if my only course of action is to do what you have done and bin/trash Xcode 4.4 and go back to Xcode 4.3.3.
Xcode 4.4 Crashing
I was runing OS X Lion 10.7.4 with Xcode 4.3.3. This ran fine and I could build and run the iOS simulator fine. I then decided on Wednesday the 23rd July to upgrage Xcode to version 4.4. From that point on when I build and run with the iOS simulator as a target, Xcode 4.4 crashed.
I then upgrated to OS to Moutain Lion 10.8 with Xcode 4.4 still installed. Exactly the same happened Xcode 4.4 would crash regardless of project or user profile.
After reading Simon (from Harrogate) comments I decided to unistall Xcode 4.4 and clean up the residual with MacKeeper.
My intentions were to go back to Xcode 4.3.3.
After the uninstall of Xcode 4.4 I did a cold reboot and then just to see re-installed Xcode 4.4 from the App Store.
I performed a re-start and then everything worked fine.
It appears there is an incompatability between the current Xcode 4.4 and OS X Lion 10.7.4.
If you do have Xcode 4.4 installed running OS X Lion 10.7.4 and perform the upgrade of the OS to Mountain Lion 10.8 this incomatabliity appears to propogate.
Upgrate OS X to Mountain Lion 10.8.
Completely unistall Xcode 4.4 (if still installed).
Clean up and residual install with the likes of MacKeeper.
Re-boot and re-install Xcode 4.4.