I dosed with 300mg of DXM and a bottle of wine last night (well, I suppose this night is over, so now two nights ago). I developed bad pressure in my eyes towards the end of the trip and for some time thereafter. The trip itself was just more sedating than usual. Not uncomfortable, but not necessary either.
Many people dislike DXM, but I find it very useful for unlocking hidden memories, which is always good fun.