I have meditated when high with great success. The key, for me, to meditating when high is to keep my awareness in my body. Being high makes that easier and fun to do. Bodily awareness can take you to some far out places!

I too, have experienced many of the states and experiences many have said keep them from being able to meditate when high. However, I consider these types of experiences as portals to the inner worlds -- and there seems to be much healing in those inner worlds.

That's my two cents.