After several builds that gave me a lot of trouble, IntelliJ IDEA build 5321 seems to hit the spot.
With several of the previous EAP builds the IDE leaked memory fairly badly and I often hit mysterious lock ups for minutes at a time. The only solution was restarting. Worse was that many times the dialog to mail exception reports to JetBrains itself would fail.
Build 5321 does not seem to have these flaws, happily, and seems robust enough for daily use.