I've spent last 3-4 hours pulling my hair as some of our sites/ sencha touch apps have stopped working properly. On further investigation and search on the internet, found out that iOS 6 - Safari seems to be caching POST requests also. Here is a small fix I did for connection request to add the caching parameter on POST requests also in Sencha Touch:

Ext.define('Df.data.Connection', {
    override: 'Ext.data.Connection',

    setOptions: function (options, scope) {
        var result = this.callOverridden(arguments);
        result.url = Ext.urlAppend(result.url, (options.disableCachingParam || this.getDisableCachingParam()) + '=' + (new Date().getTime()));
        return result;