Well, the other question is really exactly what can you DO through such a circle? If it doesn't effect YOU, then at least in theory there could be creatures not restricted by it either (IE if its not an 'all' circle). If it is vs all or natural (perhaps fey etc depending on your origin) then you're going to have some limitations on what sorts of powers you can use.
I love hearing about players using rituals in combat in creative ways. I write a weekly article about rituals and how to get more miles from them. This is right up that alley.
Well, the other question is really exactly what can you DO through such a circle? If it doesn't effect YOU, then at least in theory there could be creatures not restricted by it either (IE if its not an 'all' circle).
Of course. It wasn't meant to be impregnable to all creatures. We just got lucky in that we knew we were going to be fighting devils only, so an immortals-oriented circle did the trick.