Enable GCD update timer by default. No better time than the present to experiment with big changes.

sources/iTermAdvancedSettingsModel.m

@@ -266,7 +266,7 @@ DEFINE_BOOL(acceptOSC7, YES, @"Experimental Features: Accept OSC 7 to set userna
 DEFINE_BOOL(trackingRunloopForLiveResize, YES, @"Experimental Features: Use a tracking runloop for live resizing.");
 DEFINE_BOOL(enableAPIServer, NO, @"Experimental Features: Enable websocket API server.\nYou must restart iTerm2 for this change to take effect.");
-DEFINE_BOOL(useGCDUpdateTimer, NO, @"Experimental Features: Use GCD-based update timer instead of NSTimer.\nThis should cause more regular screen updates. Restart iTerm2 after changing this setting.");
+DEFINE_BOOL(useGCDUpdateTimer, YES, @"Experimental Features: Use GCD-based update timer instead of NSTimer.\nThis should cause more regular screen updates. Restart iTerm2 after changing this setting.");
 DEFINE_BOOL(drawOutlineAroundCursor, NO, @"Experimental Features: Draw outline around underline and vertical bar cursors using background color.");
 @end