There are already some documented methods on how to access your Google Calendar with KOrganizer.
In case you really want to have a (almost fully working) 2 way sync, you may check out the solution using the GCALDaemon that is described here. The GCalDaemon is a server that runs locally on your system that serves as a kind of proxy to Google Calendar. However it's major drawback is that it is written in Java. Thus you need to have a JVM running all the time just to be able to access the server. Well, I don't want to waste these resources on my Laptop.
Another possibility is to simply access the ICal address using a remote calendar directly. Well, this has the drawback that you can just access the calendar read-only. But for me a read-only access is OK. Google Calendar provides a nice web UI to enter events so I am fine with that restriction. I am more interested in getting Reminders for my events as I tend to forget the time while I am working.
But both solutions mentioned above have a major drawback: They only work while you are connected to the Internet. There are so many occassions, when I just wanted to check my calendar when I don't have an internet access like on the hallway when I just would like to see where the next meeting is located. So for me it's more important to have a calendar synchronization that syncs with offline data. But the solution is simple and may work not only with just KOrganizer, but with every application that works with ICS files. So here it is: