When you use grid the row selection works fine like in 2.x version, but when I add groupping:
Code:
        Scheduler.get().scheduleFinally(new ScheduledCommand() {


            @Override
            public void execute() {
                grouppingView.groupBy(columnList.get(3));
            }
        });
after click the whole view scrolls down and sometimes I'm not able to select it again. You can compare it:
http://sencha.com/examples-dev/#ExamplePlace:groupinggridexample
http://www.sencha.com/examples/#grouping