If you repeatedly have a problem receiving iMessages on your iPhone, then you should try this fix from Brian X. Chen of the New York Times. In a recent Gadgetwise column, Chen explains how he missed appointments because his iMessages were often delayed. He complained on Twitter and was counseled to uninstall Messages Beta for the Mac. Apple hasn't said anything about a potential problem with iMessages for iOS and Messages beta for the Mac, but it's an easy thing to try if you're having trouble with iOS Messaging service.
Apple OS X Mountain Lion