Absolutely not! I don't want to be hung, drawn and quartered!
My DSL connection connects to the core directly, as recommended. At the moment my Vonage box connects to the switch on the internal network, so yes it is behind the core. Of course Vonage recommend that it is put between the DSL connection and the core.
I will experiment at some point nevertheless though (but I will definitely revert it back to the LMCE-recommended setup when I start looking at other VOIP providers).